Here is the full list of all 35 Neon Abyss achievements.
Entered the abyss for the 999th times.
Died in the Abyss 99 times.
Complete a run without losing any hearts.
Made deals with Smirk Co. 99 times.
Played the Roulette machine 99 times.
Dance in the bar for 30 minutes.
Get killed by environment damage 9 times.
Defeat Argus without picking up any items.
Completes the Piano challenge 10 times.
Found 99 secret rooms.
Failed to hatch eggs 5 times in a row.
Defeat Athena in Abyssal Difficulty.
Stepped on worms 999 times.
Get killed by your bombs.
Get killed by your own bomb while in the air.
Unlock Abyssal difficulty.
Unlock 6 Characters.
Opened 999 locked chests.
Fished 10 times in fishing room.
Jumped 9999 times.
Found 5 secret rooms in a row.
Defeat God of Violence.
Empty 4 shops in a single run.
Defeat God of Machines without getting hurt.
Jump in the air for 10 times before landing.
Complete a run without picking up any hearts.
Defeat Goddess of Illusion.
Acquire 10 heart containers in a single run.
Acquire 10 shields in a single run.
Defeat the God of Electricity.
Get 50 eggs in a single run.
Defeat God of Machines.
Successfully hatch eggs 5 times in a row.
Death is another beginning.
Defeat God of Darknet.