Full list of all 101 Skul: The Hero Slayer achievements.
The base game contains 57 achievements, and there are 5 DLC packs containing 44 achievements.
Defeat the First Hero without saving the stage NPC
Keep talking to Headless
Defeat St. Joan II without getting hit
Acquire Warlord
Acquire Poseidon
Acquire Vanguard Captain
Defeat the First Hero as Little Bone
Acquire Gold Gargoyle
Acquire Carleon Commander
Acquire Minotaurus III
Acquire Elder Ent Skull
Acquire Magnifico
Stay in the black market for 5 minutes
Acquire Ghoooooul
Acquire Super Rock Star
Defeat Chimaera without getting hit
Acquire Demolitions Expert
Acquire Dark Alchemist
Acquire Sniper
Defeat the Leiana Sisters without getting hit
Acquire Joker
Keep restocking from the collector
Acquire Devil Berserker
Acquire Abyssal Monarch
Stay in the black market for 1 minute
Reach the top of the chandelier in the Demon King Castle
Rescue the Demon King and return to the Demon King Castle
Defeat the Sword of Carleon, the First Hero
Acquire Defender Captain
Acquire Destroyer
Kill 100 adventurers
Acquire Neo Samurai
Acquire Soul Knight
Acquire Nightmare
Acquire Eternal Mummy
Acquire Arch Lich
Acquire Master Ninja
Acquire Eternal Werewolf
Defeat the archbishop of the Leonia Order, St. Joan II
Acquire Royal Guard Captain
Acquire Frozen Spirit
Acquire Desperado
Acquire Dark Avenger
Defeat Yggdrasil without getting hit
Restore the Demon King Castle to its original form
Reach the top of the throne in the Demon King Castle
Acquire Yaksha
Defeat the distorted goddess, Chimaera
Acquire Gambler
Acquire Grim Reaper
Defeat the adjutants of the Gold Mane Knights, the Leiana Sisters
Acquire Champion
Defeat the elder ent, Yggdrasil
Die from a trap
Return after experiencing death
Play on Rookie Mode
Defeat the First Hero without getting hit