Here is the full list of all 30 Paint the Town Red achievements.
Defeat the Necromancer
Reach Ruin I
Unlock a permanent upgrade in Beneath
Reach Crystal Caverns I
Die for the first time in Beneath
Defeat a Shard Lord
Complete 5 Arena challenges
Complete 3 Arena challenges
Complete an Arena challenge
Complete Arena Challenge 1 in under 9:30 minutes
Complete the Saloon in Challenge mode in under 3:30 minutes
Complete the Western Saloon in Challenge mode
Complete the Pirate Cove in Challenge mode
Complete the Prison in Challenge mode in under 2:30 minutes
Complete the Prison in Challenge mode
Complete the Disco in Challenge mode
Complete the Biker Bar in Challenge mode in under 3:30
Complete the Biker Bar in Challenge mode
Complete a Scenario level without modifiers
Rescue the Apostate
Enter Beneath for the first time
Upgrade one of the Beneath classes
Reach Islands I
Defeat the Aberration
Capture the Pursuer
Destroy the Jerk
Reach The Construct
Defeat the Trickster
Reach Fire & Blood I
Defeat The End