Here is the full list of all 50 Apocalypse Knights 20 - there are The Angel Awakens achievements.
Kill 100 demons
Own 5 Broadswords
Own 5 Spears
Own 5 Lances
Kill 1000 demons with Broadsword
Kill 1000 demons with Spear
Kill 1000 demons with Lance
Own Steel Set
Own Crusader Set
Own Alloy Set
Own Nightmare Set
Own Centurion Set
Own Templar Set
Own Bloodlust Set
Own Imperial Set
Own Demon God Set
Own Ghost Set
Own 5 armors
Own 5 rides
Character level reaches 10
Character level reaches 30
Character level reaches 50
Character level reaches 100
Get 30 perfect wave
Get 100 perfect wave
Level 1 difficult all pass
Level 2 difficult all pass
Level 3 difficult all pass
Level 4 difficult all pass
Level 5 difficult all pass
Level 6 difficult all pass
Level 7 difficult all pass
Level 8 difficult all pass
Level 9 difficult all pass
Level 10 difficult all pass
Pass 20 Waves in a row
Pass 40 Waves in a row
Pass 60 Waves in a row
Save 100000 coins
100 combos
Kill 100 demons with Ultimate Skill
Kill 1000 demons on a horse
Kill 500 demons
Kill 1000 demons
Kill 10000 demons
Kill Fire Devil
Kill 100 FaceCube demons
Kill 10000 FaceCube demons
Kill 100 Raptor demons
Kill 10000 Raptor demons