Here is the full list of all 30 Paint the Town Red achievements.
Complete a Scenario level without modifiers
Die for the first time in Beneath
Enter Beneath for the first time
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
Defeat a Shard Lord
Unlock a permanent upgrade in Beneath
Upgrade one of the Beneath classes
Reach Crystal Caverns I
Reach Ruin I
Defeat the Necromancer
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