Achievements gained simply by progressing!

Containment Breach
Reach The Bonewald

I Ain't No New Recruit
Complete your first run of The Bonewald

First Encounter
Have your first encounter with an Alien

Shiny New Toy
Unlock the AR-42

Ground Zero
Reach Ground Zero of the Containment Breach

Alien Removal Division
Kill The Crusher / Complete the game

Achievements gained by killing either certain amounts of aliens OR killing Aliens in certain ways.

Sunny-Side Up
Destroy 5 Alien Eggs.
Shoot the eggs found in both The Gun Range and The Exhibit.

They... Explode
Remove 3 Divers
You have to shoot these guys, it does not count if they explode on their own.

Kaboom!
Remove 3 Aliens with 1 Grenade.
The grenade is the alternate fire option for the AR-42 (the second gun you unlock). I gained this achievement in The Gun Range, however it could also be gained on the boss fight as there isn't a lot of space for the aliens to spread out.

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Sliding Master
Remove 5 aliens while sliding.
This does not have to be during a single slide or fight, so if you just slide around a lot during fights this achievement should be easy enough.

Wallrun Master
Remove 5 Aliens while Wallrunning.
This does not have to be during a single slide, so if you just jump around a wall-run a lot during fights this achievement should be easy enough. I got this achievement during the final bossfight - I found it a bit easier due to the small fight area.

Acrobatics
Remove 10 Aliens while in the air.
This does not have to be during a single jump or fight, so if you just jump around a lot during fights this achievement should be easy enough.

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If They Bleed...
Remove your first 5 Aliens!

A Job for the ARD
Remove 50 Aliens

Alien Massacare
Remove 100 Aliens

Achievements for playing the game less! /j

King of The Bonewald + Alien Remover
These two achievements are based off of Bonewald Run Times.
For these achievements I recommend watching Speedruns[www.speedrun.com].

Certified Speedrunner
Beat the game in under 10 minutes.
In settings you can find a speedrun timer, so I recommend turning that on. Compares your current run compared to previous ones, and makes it easier for you to see where you may need to improve. Once again, I also recommend watching other people's speedruns[www.speedrun.com].

Other Achievements that don't fit into the above categories.

Gas Prices These Days…
Run out of fuel. Fuel is what allows you to wall run, double jump and air dash. Easiest way to do this is at Ground Zero - wall run until you fall.
Gas Prices These Days

Grapple Master
Grapple 3 times in a row. Below you'll find a video that shows where I got the achievement.
Grapple Master Location

You Can Run... + ...But You Can't Hide
Destroy 1/7 explosive dummies.
For these achievements, I'm going to actually direct to this guide by Lord_Flufferton!

Zero Deaths
Complete the game without dying. Try to keep your distance and basically always be moving. With a bit of practice, this achievement becomes relatively easy.

The Floor is Lava
Don't touch the ground for at least 10 seconds. Below you'll find a video that shows where I got the achievement. As you can see in the video, the water stops rising after a bit so you only have to worry about falling.
Floor is Lava Location

Or Maybe Not
From the bonewald, exit to AREA D1 and back to The Bonewald. Repeat this approximately 5-6 times.