Age of Wonders: Planetfall (PC) - Achievement - No one could survive that!

Kill 5 units with a single tactical operation

First of all, it should be noted that this achievement can be done by killing your own units in tactical combat.
There are many later game tactical operations with AoE damage - I use the 'Shredder Bomb' in this video used by The Assembly. You may find the opportunity to come across this naturally, but if you haven't and want the achievement, the Reverse Engineer produced by The Assembly should be able to help you. They can use the 'Create Construct' ability to make a weak unit next to them, so all you need is 5 Reverse Engineers to create 5 constructs, make sure they are within close range of each other and then drop 2 Shredder Bombs on them, making sure at least the same 5 Constructs are within the blast radius both times, thus simultaneously killing them and unlocking the achievement.
It should be noted that tactical operations that do not do instant damage do not trigger this achievement (eg. PyrX Bomb in the Promethean tech tree which causes damage by choking the turn after it is used)

Age of Wonders: Planetfall (PC) - Achievement - Wololo

Permanently convert 30 units to your side

A simple enough method for this achievement is to use Psi-Fish Sirens purchased from their dwellings once you enter 'Friendship' state with them on any particular map. 'Eyes of Eternity' is a good MOD to use with them as this increases their range by 2 hexes.
Use their 'Enticing Bond' ability to draw a unit in close against its will and then use the 'Impregnate' ability when the enemy unit is next to your Siren. This results in them fleeing for 2 turns afterwards and then dying, resulting in a Psi-Fish Chrysalis spawning in it's place under your command. This counts towards converting a unit.
The first Kir'Ko campaign level in the Planetfall base game is your earliest opportunity to do this method if you're playing the campaign as Psi-Fish are present and you have the option to fight Vanguard troops. Please note, this can only be used against humanoid biped targets.

Age of Wonders: Planetfall (PC) - Achievement - Line 'em up!

Use a Shakarn Deadeye to hit 3 units by using a single ability

A simple way to obtain this achievement is to use your own troops as the target. The achievement doesn't specify it needs to be enemies. This also makes it easier to make sure there are 3 units lined up. Simply arrange 3 friendly units in a line in a manual battle, then use a Shakarn Deadeye to use the 'Omni-Perforator' ability on them.

Age of Wonders: Planetfall (PC) - Achievement - The superior version

While holoshifted, use the Infiltrator to kill the unit it transformed into

This achievement is fairly self-explanatory. Simply use the Shakarn Infiltrator to transform in to an enemy unit and then get the killing blow on it in a manual battle.

Age of Wonders: Planetfall (PC) - Achievement - Hide and Seek

Over the course of a single game, find at least 15 hidden Shakarn sleeper agents

This achievement requires use of the Shakarn Tactician. The hero ability to 'Call Insider' does not contribute to obtaining the achievement as it specifies they must be HIDDEN Shakarn sleeper agents. This means you must use the 'One of Us All Along' ability of the Tactician. You can use this ability on the same unit if you prefer until it dies, as long as it's an infantry unit. It can only be used once per battle though per Tactician and can only be used after 2 turns have passed in battle, so it's best to try and avoid damage until it's usable.

Age of Wonders: Planetfall (PC) - Achievement - Make your own luck

Score 7 successful critical hits in a single round of combat

The ability to score a critical hit is based on two things - unit happiness and MOD's. To obtain this achievement I played as the Assembly as their Vorpal Snipers have the 'Vorpal Shot' ability which is a 'Power Shot' giving it a +15% crit chance. I also outfitted them with a particlar set of MOD's in the Synthesis tech tree:
- Targeting Daemon Shell: +10% crit chance (amongst other things)
- Ocular Implants(Detector): +20% crit chance (amongst other things)
- Kinetic Phase Modulator: This doesn't increase crit chance at all, but allows it to ignore 50% of accuracy penalties from line of sight and units in the way. My logic behind this being - You can't crit if you don't hit.
Depending on your race / tech, there may be other MOD's equally or more suitable, but this is a good starting point.
I did this late game after I had 'The Re-Cycle of Life' Doctrine enacted, giving all units +400 morale. I also had a good relation with my race, proving a further +200 morale, so morale of all of my snipers was maxed out.
Once the above has been done, it's just about getting the numbers in the fight - Ideally at least 3 full groups of snipers against as many enemies as possible. You may need to save and re-load as there is an element of chance.

Age of Wonders: Planetfall (PC) - Achievement - Pariah

Achieve minimum reputation

This is fairly simple and may be achieved naturally as you play the game, depending on your play style. You need at least -600 reputation to become 'deplorable'. There are several things that can be done to go towards reducing your reputation:
- Declaring war (other players and NPC factions)
- Razing cities
- Migrating cities
- Getting denounced by another player
The main things to avoid are:
- Signing any treaties with other players
- Making peace with anyone (including NPC factions)
- Avoid any positive reputation rewards from objects found on the ground
Another thing to bear in mind is to try and not raze cities of your race as this will give you a negative support bonus, lowering the overall efficiency of your colonies.

Age of Wonders: Planetfall (PC) - Achievement - Critical Failure

Make enemy units fumble 13 attacks in a single battle

Making units 'fumble' is dependent on their morale. To efficiently obtain this achievement, you need to manually battle with an enemy army that is on as low morale as possible.
To achieve this, I opted to play Huxley Wunsworth - An Oathbound Psynumbra Hero. Psynumbra tech has a few operations which cause negative morale effects. Huxley himself gets the Sinister Chorus ability after levelling up which again contributes towards giving enemies a negative morale modifier in battle. This in combination with the 'Vision of Darkness' operation stacks up to a large enemy morale deficit and both abilities are obtainable early on in a game.
It's best to make sure your using an army that you don't care about as you'll basically just need to stand there and take the hits in the hopes that the enemy units keep fumbling until they hit 13 fumbles, but with Vision of Darkness being used beforehand and Huxley's Sinister Chorus, 13 fumbles shouldn't be challenging.

Age of Wonders: Planetfall (PC) - Achievement - Friendly Fire

Kill your own unit by missing a shot

This is a little chance based. If you play the game a lot and opt for manual battles most or all of the time, you may get this playing the game naturally. I found the manual combat in this latest Age of Wonders instalment to be a bit more overwhelming than I would have liked, so got this achievement after I completed the game.
I thought it might be best to try on the tutorial level as you're given weak units and the enemies aren't particularly complex and are mostly melee, so you can learn how to manoeuvre them a little based on their responses to your actions.
The best method I found is to get one of your units on low health and just place it in front of an enemy so one of your own units friendly fires whilst trying to hit the enemy. You can also place a unit behind and sometimes an attack will miss and hit a unit next to or behind the target.
Obtaining this achievement can be a little tedious and will probably take several attempts.