This first section will go over general tips that will help for most bosses (hopefully). If there's any inaccuracies, changes, or other info that I should add to any of the sections, feel free to leave a comment, I probably got something wrong somewhere.
The ranking at the end of the match in boss fight rounds is determined by how many points you obtained during the round (Roughly as a gauge of how much you contributed.) The exact numbers are kind of weird, but the most common methods of gaining points include:

• Attacking the boss (Points gained based on damage dealt, about 100 per normal hit)
  
• Physically grabbing Group Capsules (Points based on how many players are affected by your capsule)
  
• Interacting with boss gimmicks that deal damage (e.g. knocking back Death Queen's missiles)

Elite bosses can rarely show up when doing boss battles. Most elites are similar to their base fights, but will deal more damage, have more health, stay in phases like break point for half as long, and use harder attack patterns much sooner. If you get an elite boss, don't worry about points and just try to take them out as quick as possible. Unless the whole team survives and plays well, you WILL run out of time before the boss goes down.

In Co-op battles, most skills are worthless, but there's still some useful skills you can equip. Try to put on skills that provide good movement (or that have I-frames, if you're struggling to stay alive). Attacking and Ring stealing skills don't affect the boss, and are worthless. You should also be using the Advanced Skill Equip option when you're fighting bosses specifically. There's only one mode, so the +1 Skill Level is completely free. Just don't forget to turn it off before doing normal matches if you prefer it off...

Even if you're going for #1, don't forget that you're still working with others. Spread out and cover more ground when possible. Try to occasionally hit group capsules if you feel like no one is going for them, you get points for hitting them depending on how many people are in the radius. And PLEASE, don't try to go for stronger items like thunder attack capsules and shields when you can see another player already going for them, you both can get more done if you just let them have it.

Rings are generally a non-issue for most bosses, unless you are fighting their elite variants, which can and will eat through your rings fast. Unless you are extremely low, ignore any rings that drop, you don't need them.

Death Queen is a rather basic boss, so there won't be much to list here in terms of behavior. When the fight starts, it will always lead with the missile attack (covered later) and from there all future attacks will be random (I believe). The boss will attack once from off the stage, and then will fly around the arena for the attack phase, moving to a few random positions before heading back to repeat the cycle. The boss can be damaged by finding and using an attack capsule, which can be done by either breaking/standing in the zone of one of the group attack capsules on the ground, or by breaking open one of the randomly spawning golden chests to get an electric attack capsule (note, ONLY the player who opened it gets the electric attack capsule, first come first serve). The boss has 5 weakpoints on it's lower half that take normal damage, and one weakpoint on it's head which takes more (Around triple, judging by point gain). each phase has different height gaining methods, but once you have an attack, you generally want to either use it immediately if there's one nearby/you can't get to the head, or attempt to go for the head before it escapes. as the fight progresses, Death Queen will gradually break through to 4 different layers, which will be covered in their own sections.

Death queen has 2 different attacks it can use, with an attack phase between each. this section will go over general strategies to dodge them.

Death Queen will launch several volleys of missiles, each aimed at a random player. Your missile will always be red, while everyone else's will be grey. Using a homing attack on one of your missiles will send it back at the boss, dealing a small amount of damage and giving you 100 points. Death queen will fire 4 volleys with one targeted missile per player for most of the fight, however in the final phase, she will instead fire 8 volleys with 2 targeting each player. Try not to stand in front of other players, stick near the back of the arena to give yourself time, and homing attack as soon as you can, and you should be fine.

Death Queen will start charging up several lasers which will all sweep across the arena at the same time, hitting any players in their path. If you can, try using the current phase's height gimmick to dodge over the attack, even standing on the lowered platforms in phase 4 give enough height. If you can't dodge over, do your best to find an opening and squeeze through. The sides of the arena are usually safe, so using your movement abilities here to get over there is a good call. The impact of the lasers DOES have a hitbox, so try to jump over if you need to squeeze between 2 lasers.

When enough attacks are landed on the weakpoints of the boss, they enter their "breaking point" phase. Death Queen will be knocked into the center of the arena and stunned for 10 seconds (Reduced for the elite version), which is your chance to go all out. Go to the head and land as many hits as possible. if people are camping the group attack capsules at a good rhythm, stay in the center and chain attacks, swapping sides between each to grab a new attack. If they aren't at the capsules or are at a bad rhythm for chaining, attack one side, camp the capsule until it respawns, and repeat.

As mentioned earlier, the arena has several phases depending on how far into the fight you are. this section will go over them in order.

The most basic arena. No gimmicks or anything, just a flat arena with a spring on each side for height, and occasionally spawning speed shoes in the middle. Nothing will spawn until the initial missile attack is finished, so sit around until that's over. Try to camp the group attack capsules and speed shoes near the springs, and attack the boss whenever possible.

The floor will entirely be made up of bouncy clouds, and the springs are replaced by bigger, high launching clouds. The group attack capsules will also be replaced by Buzz Bombers, and no gold chests will spawn. Instead, homing attacking one of the buzz bombers will trigger a group attack capsule effect, or will give an electric attack capsule. Try to stick near the big clouds, and attack the nearby buzz bombers for attacks. If the boss is currently busy, don't be afraid to waste your attacks and try to farm for an electric attack instead.

The floor will be coated in ice, and the two springs are attached to moving hexagons that are slightly offset from the center. Penguinators will also be sliding along the floor, although they aren't as big of an issue. This phase plays mainly the same as the Grassy Arena, camp the springs, and try not to get hit by the Penguinators or the boss. If you're having trouble hitting the spring, try to cut it off by going in front of it instead of heading right for it.

In this phase, the floor will be covered in a star shaped pattern of timed retracting spikes, going outward from the center. The speed shoe capsules from the first phase make a return here, and the springs are replaced by platforms that periodically move up and down. Landing a hit on the head in this phase is hard, so try not to go for it unless the platform cycle lines up at the end of an attack, otherwise you're wasting time waiting for the platform. The boss will also start using harder patterns of the laser attack, and 2 volleys of missiles. Just hold on until the fight finishes and you should be good.

1. Go for the head when possible
   Going for the head, while slightly slower, does triple the damage and gives triple the points for each hit. Stay by the height gimmick, and get hits in as often as possible during attack phases. Unless you don't think you can make it in time, or you aren't in a good position to go for it, you should prioritize headshots.
   
2. Ignore tip #1 (Kind of)
   Yeah, that's right, you SHOULDN'T always go for the head when given the opportunity. If you manage to get your hands on an electric attack capsule, you should attack the bottom of the boss instead. the AOE shock will hit all 5 weak points and occasionally even the head, meaning you will get at minimum 500 points from the attack, compared to the 300 from the headshot hitting nothing else. In the Cloudy Arena, use this as much as you can. a double jump from a floor bounce can reach the Buzz Bombers, so try to cycle through as much as possible when the boss attacks to get an electric attack capsule. During this phase's break point, stick near the back of the boss on either side, then attack, double jump, homing attack the nearby Buzz Bomber, attack again, repeat. If you can chain it well enough, you can get a ton of hits in, and if RNG is in your favor, you'll do massive damage from all the electric attacks.
   ALSO, during the final phase, the platforms take a long time, so you shouldn't use them unless they line up with when the boss finishes their attack, it's better to just get a bunch of weak hits in.
   
3. Some small optimizations
   Whenever you have free time, mash the action button as much as possible to automatically hit any gold chests nearby when they spawn. The only times you shouldn't mash are when you already have one, and during Phase 2 when they can't spawn. Also, at the start of the battle, if you time your launch off of the spring right, you can hit the first missile while being low enough to be in the group attack capsule area, but high enough that you can hit the boss when they approach. This is very rare, as you have to rely on getting a late missile during the first attack, your teammates hitting the capsules, AND the boss heading to a spot nearby, but if you can pull it off, you can get a good headstart.

These Power Ranger knockoffs are technically 5 separate enemies with their own health bars and attacks. This section will go over things consistent between them.
The Egg Pawn Rangers work like most other bosses, only able to be attacked with an attack capsule or electric attack capsule. Each Egg Pawn Ranger will start the match on one of the many random platforms in the map. They will each stay in that section for a set period of time, using attacks every so often, and then teleport away to another random platform. Each Egg Pawn Ranger has 3 actions they randomly pick between every time they get an action. generally, each has a small attack, a big attack, and the ability to spawn enemies. They will also gain a short shield after each attack. All enemies spawned by any of the rangers have a small chance to trigger a ? capsule effect when defeated, giving either an attack capsule, shield, or very rarely, an electric attack capsule.
When a ranger falls a little under half HP, they will cease attacking and teleport away. once all 5 are gone, a spring will spawn in the middle of every platform that launches you to the final arena. Here, all 5 Egg Pawn Rangers will be roaming and attacking at once, and they will not teleport away again until they die.
The arenas feature a lot of group and group speed shoe capsules, so use that to your advantage. Gold chests also occasionally spawn at bridges between platforms, but from my experience they only contain rings, so it’s best to ignore them. Try to form small groups and target a specific ranger. If too many people are on one, swap to a different one. If you're in a call with friends, every platform is marked with it's row and column to call out locations if you need to.
Each Egg Pawn Ranger has it's own set of elemental attacks and enemy spawns. This section will go over all of them individually.
Red wields a lance, uses fire attacks (more damage? haven't checked)

• Small attack: Lance charge
  Red will prepare a lance charge and rotate to track a random player. After a short while, he will lock on and charge in the direction of the indicator on the floor, hitting any players in the way.
  
• Large attack: Fireball
  Looks similar to lance charge, but the floor indicator will not rotate. After a brief period, Red will shoot a slow, lingering fireball in the direction indicated.
  
• Enemies: Cluckers
  They stay still and occasionally pop out and shoot a projectile. Hit them when they pop out to shoot.

Wields a Katana, uses electric attacks (extra hitstun)

• Small attack: Electric Slice
  A large semicircle indicator will show up in a direction. After a brief delay, Yellow will swing, launching a fast moving, long range projectile along the floor. You CAN jump over it, so don’t waste time running away.
  
• Large attack: Electric Spin
  A large, circle indicator will show up. After a bit, Yellow will spin and drag their sword along the ground. Just play jump rope with him for about 3 spins when the attack ends.
  
• Enemies: Thunder Spinners
  Hover in place and occasionally put out an electric shield. Be patient and homing attack when the shield goes down.

Green uses a club, and wind attacks (extra knockback)

• Small attack: Club swing
  Simple, overhead club swing. Green Turns to face a direction, and then slams down their club, launching a wind projectile forward that covers extra range.
  
• Large attack: Club rush
  Like club swing, but with a wider hitbox and more rapid. Green turns to a direction, Slams and launches a wind projectile, and repeats 3 more times.
  
• Enemies: Buzz Bombers
  They're Buzz Bombers, I don't know what to say. Dodge any projectiles and hit them for free stuff.

For his neutral special, Blue wields a gun (and ice attacks, that put you in some king of snowgrave an ice cube. Mash the action button to get out.)

• Small attack: Gun
  Blue shoots a slow turning homing projectile at a random player that follows for about 9 seconds. Make turns often and take advantage of the slow turn.
  
• Large attack: Blizzard
  3 Circular indicator rings will spawn. After a few seconds, a blizzard will appear and sweep in a circular pattern along the rings. Just stand between the rings or in the blind spot at the center and you'll be fine.
  
• Enemies: Crabmeat (for some reason)
  Literally just fodder. Homing attack for more free items.

Purple just throws hands, and uses poison (slow effect on hit, cleared by any other timed effect (e.g. shield, speed shoes) or by waiting)

• Small attack: Rushdown
  Purple rushes forward while slowly turning toward players, trying to grab and hit anyone in their way. Just keep your distance.
  
• Large attack: Ground Slam
  A big indicator appears as Purple charges up. After a bit, they will jump up and slam down, covering the ground of the entire indicated area with a slowing effect for a brief moment. Jump over or get out.
  
• Enemies: Caterkillers
  Pop out, shoot a projectile, retreat. Like Cluckers, but bigger, use the same strategy.

I have less experience with this one, so I don't have much advice.
Try to stick in small groups to avoid crowding and item stealing. Swap targets if necessary.
Try to keep speed shoes as much as possible, as the Rangers move around a lot.
Electric attacks aren't too useful outside of the final phase, and even then they usually aren't worth it. Unless there's a good opportunity, just keep attacking.
All of Yellow's attacks can be jumped over, and you can run circles around Green and Blue, so keep close to them when you can. Purple’s grab and Red’s Lance charge make staying close to them riskier than the others, but it’s still possible.
BE PATIENT!!!! Wait for the shields to go down, don't mindlessly mash attack. You will waste your attack AND get hit.