Here is the full list of all 16 Demons with Shotguns achievements.
You collected 500 souls!
You earned 3 Monster Kills.
You don't seem to understand how ammo pickups work.
You completed Ghosts n' Nomeds.
You're an a' hole with how much you taunt.
Flawless Victory!
You earned 5 Double Kills.
You earned a Antichrist kill streak.
You kept killing yourself.
You used 10 tarot cards in one match.
You jumped 100 times in one match.
Fighting for scriptures.