Here is the full list of all 64 Relapse achievements.
The base game contains 57 achievements, and there is 1 DLC pack containing 7 achievements.
Upgraded every talent to max level
Defeated Dragon
Defeated all act 3 bosses
Defeated all act 3 elites
Defeated Ogre Shaman
Defeated Ogre Warrior
Defeated Ogre Bandit
Defeated all act 2 elites
Defeated Obsidian Golem
Reached max level with Elementalist
Reached max level with Ritualist
Reached max level with Berserker
Defeated Rune Keeper
Defeated Slime King
Defeated Blue Guardian
Defeated Green Guardian
Defeated Red Guardian
Reached max level with Crusader
Defeated Slayer
Defeated Reaper
Defeated all act 2 bosses
Defeated Necromancer
Defeated Dragonkin
Defeated all act 1 elites
Defeated Forsaken
Defeated Warlock
Defeated Leshy
Defeated all act 1 bosses
Reached max level with Beast Master
Defeated Bandit
Defeated Lich
Defeated Elite Guard
Defeated Fungi Mage
Defeated Fungi Bandit
Defeated Blue Spirit
Defeated Red Spirit
Beat Act 3
Defeated Djinn
Defeated Blue Drake
Defeated Undead Warrior
Defeated Elemental
Defeated Mech
Beat Act 2
Defeated Werewolf
Defeated Jakki Mage
Defeated Jakki Bandit
Defeated Titan
Defeated Earth Demon
Defeated Spider Queen
Defeated Cyclops
Beat Act 1
Defeated Bone Golem
Defeated Ifrit
Defeated Treant
Defeated Hobgoblin
Tutorial completed
Knows a good deal when they see one
Beat Ascension 7
Beat Ascension 6
Beat Ascension 5
Beat Ascension 4
Beat Ascension 3
Beat Ascension 2
Beat Ascension 1