The guide that covers all achievements. Also spoilers be warned.
How to Obtain All Achievements
- Cauterize your wounds
- Fire the revolver
Found on the corpse after the area with 2 monsters and 1 save location, it is on the next area where you must go around the corpse. The bullet takes 2 bar slots.
- Kill a mutated scient[e]st
After you have a revolver, they do take 4 bullets to be killed.
- Kill a mutated lab rat
You first encounter the mutated rat after you press the green button. They are easy to kill but annoying to deal with.
- Fire the double barrel shotgun
As you progress through the game, should be found with 2 save points on it after you exit the hallway. Then like the revolver kill the monster. The shell takes 6 bar slots
- Fire a flare
Use the flare gun on the hordes. The flare ammo takes 14 bar slots
- Kill a corpse trap
You can use 2 shells or 1 flare on them but I think I would not advise using the revolver since you need the ammo.
Big Game Hunter
- Kill a mutated lab monkey
When there are 2 corpses and 2 Monkeys locked inside the glass container, your flare gun is the best option, note that flare guns can ricochet when I hit the Sleeping Beauty aiming to the right and it hit back to the Monkey. Use 2 flares against them. There are also few of them as you progress but it’s best if you do it where they won’t attack you unless you get to the last one which is the biohazard area where there are so many crossbow bolts on the walls.
- Fire the crossbow
In-game it’s called Medieval according to the Achievement tab on the menu. The crossbow can be found after the Hunter encounter at the beginning of the next level. Thankfully it does not use your slots but you can only carry 3 crossbow bolts in total unless you loaded one on your Crossbow as an extra.
It can kill the following enemies:
- Mutated scientist and rat in 1 shot.
- Sleeping Beauty in 2 shots.
- Mutated lab Monkey should take 3 shots also.
- Hunter are an exception but you can stagger the Hunter with it.
- Stagger the teleporting hunter
Wait for the Hunter to teleport and once he stops charging shoot it quick with the crossbow, an animation plays a little bit and then you will get the achievement after he teleports once again
- Kill the hunter for good
This is the final boss against the hunter from what I presume is either a Prologue or Act I. A shotgun is a preferable option on each corners and watch out for those eggs the Hunter spawns. Thankfully you slide slightly faster and there are items like the eggs spawns them.