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