Anyway, for the normal infinite on Wario, I've never seen the data nicely compiled so I did my own research with much better methods than the last time I tried. I manipulated two controllers to try to double jump out and to try to air dodge out (in case Wario gets grabbed when he has wasted his double jump). Wario's situation is really not that bad. If anyone discovers any mistakes, please let me know. Of course, those wily Wario mains like to be hush hush about the infinite so if I did make mistakes you can be pretty sure they won't tell you.
Infinite with Double Jump:
Bowser*, Yoshi*, Zelda*, Zero Suit Samus*, Pit, R.O.B., Fox, Falco, Wolf@
Infinite without Double Jump:
Diddy Kong, Meta Knight
Not Infinite:
Mario, Luigi, Peach*, Donkey Kong*, Wario*, Link (t), Sheik*, Ganondorf*, Toon Link (t), Samus (t), Ice Climbers, Kirby, King Dedede, Olimar, Captain Falcon*, Pikachu, Squirtle, Ivysaur*, Charizard@@, Lucario, Jigglypuff, Marth*@@, Ike*, Ness, Lucas (t), Mr. Game & Watch, Snake*, Sonic
*: Can force a jump break on Wario on flat ground.
@: Wario gets a chance to use his double jump, but he gets grabbed before he can ascend.
@@: Wario's double jump turns into a footstool, allowing him to escape what he otherwise would not be able to.
(t): These characters have tethers that aim down slopes and fail pretty horribly at regrabbing Wario. It's novel so I thought I'd note it.
By the way, Yoshi players, don't pummel Wario immediately after you grab him. If you avoid that, he can't ground break. Zelda and Bowser have very slow pummels; if you can mash grab breaks fast enough as Wario, you can probably make their "infinite" do no guaranteed damage at reasonable percentages (which means that you could call a TO over and make them let you go due to stalling). Regardless, all of them are pretty tricky to do; don't expect to pick up these guys as secondaries to beat Wario since you won't. Consider this a nice bonus if you already main a character who can do it.
For those who want to use stage counterpicks to help with this, here are all the stages with slopes that might reasonably be legal.
Permanent slopes:
Yoshi's Island Brawl (only on the VERY edges... and the platform sometimes), Skyworld, PictoChat (only on the VERY edges... and some drawings), Green Hill Zone, Yoshi's Island Melee, Onett, Corneria
Interrupted slopes:
Mario Circuit, Pirate Ship, Distant Planet, Brinstar
Temporary slopes:
Delfino Plaza, Lylat Cruise (not useful at all), Pokemon Stadium 2, Castle Siege, Rainbow Cruise, Pokemon Stadium 1
And more stage fun... Low ceilings doom Wario. On Luigi's Mansion, I'm pretty sure every character who can force a jump break has some regrabs on Wario except Marth who steps forward when he grabs and will eventually lead Wario outside of the house. On Skyworld it's even worse because you have a low ceiling above a slope; don't get grabbed with Wario there!
To be fair to Wario, he can avoid all of these infinites by hanging under low platforms. Battlefield, Norfair, Frigate Orpheon, Halberd, Lylat Cruise, Pokemon Stadium 2, Distant Planet, Smashville, Jungle Japes, Onett, Green Greens, and Pokemon Stadium 1 offer large amounts of such opportunities. On Smashville, he's pretty much infinite proof!
Lastly, I only tested the use of standing grabs. Using dash grabs or pivot grabs may enable further abuse though do be warned that they risk tripping. I'll leave that as an exercise to the reader to discover.