Here is the full list of all 33 Johnny GravesThe Unchosen One achievements.
Defeat Satan
Finish the Catacombs and find the Tomb of Azazikiel
Finish the Catacombs without dying
Finish the Cathedral without dying
Finish the Cathedral
Defeat Father Patrick without taking any damage from his spells
Finish the Graveyard
Finish the Chinatown part 2
Finish Chinatown part 2 without dying
Finish the Chinatown part 1
Finish Chinatown part 1 without dying
Finish the Station
Defeat Dh'aniyel
Finish the Subway
Die
Finish the Graveyard without dying
Finish the Subway without dying
Finish the Station without dying
Finish the Graveyard without taking any damage
Finish the Cathedral without taking any damage
Finish the Subway without taking any damage
Finish the Station without taking any damage
Finish Chinatown part 1 without taking any damage
Finish Chinatown part 2 without taking any damage
Finish the Catacombs without taking any damage
Clear Cathedral without using Health pickups
Kill a Hellhound with a Golem
Kill 10 enemies in under 2 seconds
Have a single Necromancer revive at least 10 zombies
Cause at least 4 zombies to be caught on fire simultaenously
Kill at least 3 different types of enemies with a single Ricochet shot
Cause Father Patrick to kill one of its minions
Kill 3 zombies with an explosive zombie