Devil May Cry 4

Beat up to and including level 20 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 11-20:

11 Assault x 2
12 Mega Scarecrow x2
13 Assault x2, Bianco Angelo x2
14 Faust x1
15 Bianco Angelo x2, Alto Angelo x1
16 Scarecrow x6, Mega Scarecrow x1
17 Alto Angelo x2
18 Blitz x1
19 Basilisk x4
20 Berial (Boss)

complete up to floor 20 (berial being the boss) of bloody palace
dont quit you must either get a game over or finish the palace (101) and will unlock at the results page.