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