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