Devil May Cry 4

Beat up to and including level 50 in Bloody Palace mode. To unlock Bloody Palace mode, beat the game on Devil Hunter difficulty. Do not quite the game, you need to die or finish all 101 floors to get the achievement. Below are a list of the enemies from waves 41-50:

41 Chimera Seed x9
42 Chimera x5, Chimera Seed x5
43 Chimera x4
44 Chimera Seed x6, Gladius x6
45 Chimera x2, Blitz x1
46 Basilisk x2, Chimera Seed x4
47 Chimera Seed x5, Bianco Angelo x2, Alto Angelo x1
48 Scarecrow x1, Chimera Seed x6
49 Chimera x3, Faust x1
50 Scarecrow x6, Chimera Seed x12, Assault x4

Complete up to floor 50 of the bloody palace but do not quit you have to either finish the palace or get a game over it will unlock at the results screen