I don’t know if they were the MOST obnoxious. That bar is set mighty high. But I can guess that these six were undeniably obnoxious, even though I have never seen a minute of any of them, and I had mercifully forgotten about some of them.
My guess is that some others were equally bad or worse, like:
“I’m a Celebrity, Get Me Out of Here”
All of those “Real Housewives” shows – isn’t obnoxiousness their whole point?
“The Elderly Bachelor” (whatever the real name of that thing is)
“The Surreal Life” – Wasn’t that the one with Mini-Me, Flavor Flav, the Willis daughters, Brigitte Nielsen, Gene Gene the Dancing Machine, Oscar Pistorious, Tammy Faye Baker, Gadabout Gaddis, Vanilla Ice, Potsie, Rudy Giuliani, and several of Jeff Dunham’s puppets all living together in a special “failure’s quarters”? I’m kind of sorry I never watched that one. (OK. I made some of those names up. I think the first two are real, maybe some of the others.)

My fave was an in-universe one on the Simpsons – Promiscuous Idiots Island. The twist was that they weren’t on a real island, it was a peninsula.
“That’s IT! I’ve had enough, I’m on the next plane out of here!”
“You don’t have to wait, you can drive.”
“WAAAAH!!”
lol. I missed that Simpson’s episode, but that’s solid.
The Surreal Life was dope. In a later season, a really hot Real World and/or Road Rules standout went topless. Across the table from Ron Jeremy I think.
Her name was Chantelle something or other and she even did a Playboy shoot. She was a bombshell!
6. Keeping Up With The Kardashians popularity shows what a messed up country the US is and Seacrest is a discerner of that culture.
There will be a special place in Hell for Ryan Seacrest. He is just downright…. EVIL. The same level of Evil as our dictator.
Straight Plan for the Gay Man, a spoof on Queer Eye for the Straight Guy, with Rob Riggle was priceless.
“The Swan” was in pretty bad taste (pun intended).