The Original Meme was made on YouTube by Ale Fabius.

I'll name off some more dangerous or mental hazardous levels here.
The Dark Metro
-(2⁶³-1) or level [REDACTED]
The Insulation
End Of The F#c*ing World
The Military Hospital (other level 14)

Level 999
Level -998
"Paradise (Level 14: The blood-stained forest)"
Level -2
"The Grand Illusion"
Level 400: "M1nd is s0ftwar3"
Level 404
Level 69
Level 420 (yes these levels are actually dangerous lol)
Level 611: "The maze, the creatures, the monster"
Level 666: Welcome to hell
Level 38: Fold Point
Level 78: Space Station as of the death of the neutron star protecting the level (see Null-06 and Entity 404).
Level 42: The Eternal Wait
Level 42: "The Horyzon" or what I like to call "Unnatural Disasters"
Level 74: "stage fright"
Sublayer 1.1

Since I'm tired I won't mention anymore for a while. Hope this helps!

Thanks. That did help a lot.

no prob.
If ya want I can explain what each of them are like to live in.

Sure.

aight.
The dark metro, you gotta hide constantly, there's a cult that needs outsiders to sacrifice to their satanic train.
Level [REDACTED] is the most mentally terrifying level apparently, and is accessed from a few special entrances from specific levels and also from noclipping during quantum fluctuations in the void. There are no exits. You're screwed. You can't do anything to save yourself now.
The insulation contains many different entities, and the deep insulation has the crawlspace creature; it's smarter than what people say. Don't go into the deep insulation casually.
End of the frickin world is the end of the frickin world. You got your normal entities for a chaotic level and special bandits that are smart and wield weapons. Avoid at all costs, though that's pretty easy as the only way here is via the blue channel.
The military hospital is a military hospital. From the 1800s. I don't know much about it but it doesn't pose too big of a threat, just a weird level. Seek help from the group here, they've figured out how to exit this level.

999 is a mentally hazardous level where to leave you must either be broken by voices or apologise for your doings.
-998 is a level thought to be a pocket dimension ruled by entity 100. It's class contested: non-human, where we aren't superior beings. Try to survive until you're sent back to the level you were at, though this place is a slight deadzone as the air is heavily polluted, I think.
Paradise is a trap level. Don't go there.
Level -2 has a pattern of chaos. That's all I got to describe it.
The Grand Illusion is a level that switches from class 0 to class 5 every 50-60 minutes; don't stay around for more than those 50 minutes.
400 is a level inhabited by the Coders who are a danger to everything in their level. They'll attempt to convert you on sight.
Level 404 is a really weird level. It's a very glitchy heaven, some say. It's also disorienting. Don't know what to say.
Level 69 is a road trip gone wrong, and now you must drive. DON'T LEAVE YOUR CAR; IT WILL GET YOU KILLED.
420 is a freezing level, nothing normal can, will, or should live here.
611's name checks out. It's a maze filled with entities and a powerful beast that knows where you are as soon as you appear in the level. Just don't come here.
666 is based on DEALS. Destruction, Entities, Audio, Light, Sanity. These will adjust to make the person who is here feel they truly are in hell. -Out of room-

Fold point is chaos of the first 38 levels combined. You could come here while noclipping on accident.
Level 78 is dominated by a black hole.
The Eternal wait is not well known to me but I'd bet it's a wait for eternity.
The Horyzon / Horizon is a chaotically disastrous level with environmental hazards.
Stage fright is a weird level that is normal for 2 hours before you rapidly go insane.
1.1 is a hallway becoming progressively more dangerous as you go along, from 0 to 2 to 4 to deadzone and then anomalous. Wouldn't recommend coming here. Ever.