Here is the full list of all 38 Red Haze achievements.
Got Ending P!
Got Ending F!
Got all 26 endings in Red Haze and went through the Alphabet Door.
Got Ending A!
Got Ending B!
Got Ending C!
Got Ending D!
Got Ending E!
Got Ending G!
Got Ending H!
Got Ending I!
Got Ending J!
Got Ending K!
Got Ending L!
Got Ending M!
Got Ending N!
Got Ending O!
Got Ending Q!
Got Ending R!
Got Ending S!
Got Ending T!
Got Ending U!
Got Ending V!
Got Ending W!
Got Ending X!
Got Ending Y!
Got Ending Z!
There's a lot of secrets, but this one might just be the most well hidden...
Failure is always an option.
You decided to strut your stuff.
Met up with Aunti G.
Took Starry's dress for your own.
It gets worse here everyday!
Exit: Hope
Listened to a Cassette Tape.
Saved 1000 times total and went to the Save Shrine afterward.
Defeated the Abomination.
Went to the Other Place.