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