Here is the full list of all 52 Bite the Bullet achievements.
Unlock your first wow node
Complete all the tutorials
Unlock the Gorivore Class
Unlock the Slaughterer of the Soil Class
Unlock the I See, I Eat Class
Unlock the Smorgasborg Class
Consume 10,000 calories
Consume 100,000 calories
Consume 10,000 protein
Consume 100,000 protein
Consume 10,000 fat
Consume 100,000 fat
Eat 20 lightning geckos
Vomit 10 times
Craft you first gun
Get your first shotgun
Get your first critter cannon
Get your first flamethrower
Get your frist missile launcher
Get your first rail gun
Eat 30 camo ghouls
Complete the minotaur quest
Beat the Gigavulture
Beat the Flesh Golem
Beat the Snatchoid
Beat the BC3K
Beat the Mastermind
Beat the SAMNG
Beat the Eyeful
Beat the Trinomorph
Fully upgrade every gun
Eat every type of plant
Eat every type of enemy
Eat every type of robot
Wear 4 different bandanas
Block 500 rounds with the shield
Talk to 3 different janitors
Complete the Bucephalus quest
Kill 4 enemies with one round
Use a fire effect on a medbot
Defeat 10 enemies with fungus bombs
Kill 10 enemies with vomit effects
Shot 10,000 Rounds
Reach Level 20
Get 20 nodes in the same branch of the skill tree
Kill ten enemies with body shrapnel
Eat 10 projectiles with the Appetite for Destruction ability
Stay invisible for 20 seconds
Deal 100 damage with the thorns ability
Slow down 100 projectiles with the Expanded Consciousness ability
Use a trampoline critter, then double jump, then air dash
Dash 10 times in a row