Here is the full list of all 11 Doomies achievements.
Get S Rank in the Game Over screen
Get A Rank in the Game Over screen
Reach the "Police" stage!
Unlock a hat!
Get a x50 combo!
Get a x100 combo!
Get a x150 combo!
Get a combo upgrade with the Espasmo-12 shotgun
Get a combo upgrade with the Cuerno-47
Get a combo upgrade with the Chairo-556
Get a combo upgrade with the Trench gun