The plant one from new Vegas. 83? It's so messed up.

If you don't have time to read the wiki page, basicly this vault was given a GOAT to see if they could make vegetation in the Mojave, but as they are working a sickness or a gas infects one of the scientists and it starts. But instead of dying they are turned into spore carriers that are the form or residents. Scary as heck.

There are many, many Vaults which did terrible physical and phycological things to the residents, and all are competing well and coming to a near enough tie.

I would agree that 11 or 87 are two of the worst of the lot, for very different reasons.

Vault 11 is one of the worst of the psychological traumas because it made the residents active participants. Unlike so many other vaults, where a secretive group of scientists and administrators worked against the interest of those in the vault, in 11, we see the residents forced to turn against themselves. They were made to believe systematically sacrificing their loved ones was the only way to keep the rest of the population safe, and so they destroyed each. The vault is filled with remorse and guilt.

With 87, it is another body horror vault, but what has made it so terrible is that the super mutant population escaped, and have spent 200 years killing and mutilating survivors across the Capital Wasteland. The story of how things went wrong? Unlike other vaults, it didn't just end when the residents and staff fell apart. Those mutants are still out there, making new victims.

^^ That's Vault 22, and it's definitely one of the worst, not because the experiment itself was intended to be extremely cruel but because it went so horribly wrong.

I believe it was one of vault tecs only real step toward rebuilding the world.

the school one in FO4. They slaughtered all the adults and tortured little kids into soldiers and when they finally turned 18, were they too were killed and their genes were “harvested”

Vault 43. Was just senseless violence, no real justification or excuse to be made unlike most other Vaults where there was some somewhat coherent endgoal to the trauma.

It tests the most important question: can 30 people beat a panther to death before it learns how to open doors?

I want to say something more poetic like Vault 43 is an allegory, a microcosm, with our 30 dwellers representing the last of humanity facing off against the harsh and unyielding wasteland, as represented by a panther... but what fucking sense would that make? Little fucking late to test that when it runs concurrently to the actual end of the world. Though given the vault track record of folks not reporting, it would be somewhat hilarious if the panther did not actually arrive, and one of the worst designed jokey vaults actually went on to be one of the safest.

Or if they messed up and it was just one guy and 30 panthers.

Vault-Tec not only messed up in having an unreliable delivery driver, but did not check if the panther was pregnant. What remains of suburban Hoboken, New Jersey now has a native panther population.

Vault 11 is definitely the winner for me because as a few others said, the Vault residents were actively involved in the decision-making in this “experiment,” leading to incredible psychological trauma.