Here is the full list of all 52 Skeleton Crew achievements.
Complete one level within the target time
Complete every level within the target time
Get all score bonuses on one level
Get all score bonuses on every level
Earn a 'deathless' award on one level
Earn a 'deathless' award on every level
Find all the orbs hidden in one level
Find all the orbs hidden in every level
Earn all the end of level awards for one level
Earn all the end of level awards for every level
Fought your way back to YEET HQ
Defeat the mummy lord and begin the fight back against the undead
Fight your way through the castle prison
Defeat Cichol and reclaim Boneridge Castle
Conquer the underworld arena
Defeat Lord Ordog the Forge Fiend and halt the demonic invasion
Escape the clutches of the witches' coven
Defeat The Hooded Carrion
Defeat Cowl and restore him to his senses
Free Tristesse and give her a new purpose
Find every piece of Calaca and put him back together
Unleash Teufel and prepare for chaos
Destroy Lila's demonic contract and liberate her from the arena
Rescue Byron from captivity
Pull Gimbal out of trouble
Help Grodel snap out of the Hooded Carrion's spell
Cook up an interesting concoction to summon Gilliam
Complete the main game to have drinks with Drago
Reunite with Yvaine and learn of Cowl's fate
Crush an enemy with a boulder
Slay an enemy by kicking them into an environmental hazard
Defeat 5 enemies with a single kick
Kick a chicken into fire. You monster
Kick an enemy with a cabbage stuck to their head
Obtain all orbs in Fort Pellant
Protect all the wagons leading up to the Castle in the Outlying Farms
Rescue all the villagers trapped in the burning buildings of Boneridge Village
Break out all prisoners in the Prison Escape in under 3 minutes
Complete the Castle Siege without being hit by any of the trap towers
Ride the elevator in Ascent to the Keep without killing any enemies and without losing a life
Release all the caged elves in Descending the Chasm
Complete the Lava Caves without touching any fire, coal or lava hazards
Make it across to the other side in Demonville
Defeat 5 enemies in the Infernal Temple by using saw blade hazards
Break the Hell Forge in under two minutes
Use mushrooms to defeat 5 enemies in Fennygap Village
Crush 5 enemies with logs in Crossing the Swamp
Pacify 10 wyverns by feeding them meat in the Witches' Camp
Get through the wyvern nursery without breaking any wyvern eggs in the Wyvern's Nest
Get surprised by a Mimic
Slay an enemy by kicking another player into them.
Blow up an enemy by kicking a TNT barrel into them