Bryon

I wouldn't be surprised if Tirek is one of the worst, considering he possesses the power to drain magic and to make himself even stronger. I could imagine that there might be much worse than him, but he's one of the tops of the list.

Still, I wonder in About Time, how the heck did Cerberus get out of Tartarus??
LanceOmikron
Wallet After Summer Sale -
Artist -
Magical Inkwell - Wrote MLP fanfiction consisting of at least around 1.5k words, and has a verified link to the platform of their choice
Not a Llama - Happy April Fools Day!

Because COLORING!!
I never believed for a second that Tirek was the only baddy trapped down in Tartarus.

Seriously, one of the season finales has to involve a mass breakout from Tartarus. That's the only way to truly top Tirek.
Background Pony #C170
io would have to say………… quite likely ther are worse than even tirek.
Background Pony #BEEF
@Poptard
And you'll only see that kind in fanfiction.
Evowizard25

@Poptard
Given the state ponies were in after being drained, I think they'd die out soon.
BigBlueberry

@Sixtyfour215
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archestereo

…ya know, it would be cool if they made tartarus like an scp sort of thing; I mean, Tirek takes magic for himself and has to remain isolated, hypothetically the smooze would be something they'd have to keep locked watertight, and I bet they could even do their own spin on the "weeping angels."
Poptard
Every pony has fans - Derpi Supporter
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The End wasn't The End - Found a new home after the great exodus of 2012

The Tastiest
Honestly, I'm surprised more people don't believe this. Tirek was mean, but he apparently didn't go out of his way to kill anybody who wasn't an active threat, and in the end he just wanted to control everything and not be opposed. There's probably monsters in Tartarus who enjoy causing actual suffering on ponies, associated sadists, kaiju or something, or Ragnarok or other world-ending threats.
Psychopomf
The End wasn't The End - Found a new home after the great exodus of 2012

@Background Pony #5BCE

I also hope they have some guards in there.

Probably Lunar ponies that come across as very depressing or antisocial.
RainbowDashie41

@Thanotos Omega
Cell Frieza Cooler Broly
albert19
Magical Inkwell - Wrote MLP fanfiction consisting of at least around 1.5k words, and has a verified link to the platform of their choice

Maxila
Spike's mom is in there I bet.
Background Pony #97C8
It's About Time:
But if he's here, then all the ancient evil creatures that have been imprisoned there can escape and destroy Equestria!

Wikipedia, Tartarus:
…the deep abyss that is used as a dungeon of torment and suffering for the wicked and as the prison for the Titans.

Don't know about any of them being worse, but that Tirek's not the only guy there's pretty much a given.
Aurora Moon
Economist -

@Thanotos Omega
Ivan Ooze. Hah.
Thanotos Omega
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They/Them if you please,
@Sixtyfour215
@Sixtyfour215
@Sixtyfour215

T-T-TRIPLE POSSSSSSSSSSSSST!!!!!!!!!
Sixtyfour215
The End wasn't The End - Found a new home after the great exodus of 2012

Sorry about reposts. :(
Sixtyfour215
The End wasn't The End - Found a new home after the great exodus of 2012

Maybe that Goat villain from G1? I forget his name.
Sixtyfour215
The End wasn't The End - Found a new home after the great exodus of 2012

Maybe that Goat villain from G1? I forget his name.
Sixtyfour215
The End wasn't The End - Found a new home after the great exodus of 2012

Maybe that Goat villain from G1? I forget his name.
Thanotos Omega
Wallet After Summer Sale -
Not a Llama - Happy April Fools Day!

They/Them if you please,
Other things locked in Tartarus may be, Smooze, Grogar, Dio Brando, Mummra, Hordak, Venger, Unicron, Ivan Ooze, Hitler, Seeth The Scaleless, The one Pokemon you made when you were six, the usual,
WyrmSpawN
Thread Starter - MLP G5 Discussion and Speculation Thread
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Abandoned By Hope
Who knows who else took advantage of the doggie guard's break?
Space Pirate
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I regret nothing
Is Unicron down there?