Here is the full list of all 15 FLERP achievements.
Survive for 30 minutes
Survive for 30 minutes in NG+1
Survive for 30 minutes in NG+2
Survive for 30 minutes in NG+3
Survive for 30 minutes in NG+4
Survive for 30 minutes in NG+5
Survive for 32 minutes in any difficulty
Reach Player Level 5
Reach Player Level 10
Reach Player Level 20
Reroll the shop 1,000 times
Level up a tier 4 unit to level 3
Defeat 100,000 enemies
Defeat 1,000,000 enemies
Defeat 1,000 Zapper enemies