Onslaught consisted of people far wiser and more experienced than Franky like Magnus and Charles so I'm not sure; his imagination may not be as expansive as it was when he was Onslaught.
Imo, between Jaspers and Braddock, particularly considering that the "Take Jaspers to Unspace to neutralize him" weakness is only known by 1-3 beings in the universe (The Fury, who wasn't exactly talkative, and possibly Merlyn and Roma), so no one else would know to do that in a fight. Also, that's the epitome of PIS because while in unspace he still had his own mass and the Fury's to manipulate so, technically, he shouldn't have been depowered.
i'd list mjj, braddock or wanda and in that order...
mjj whose only real opponent was the fury
braddock for making even his sister immune to reality altering events
wanda for the hom catacylsm.. but... since it was possibly amplied for the events in excalibur.. can't really put her up there with the other two...
onslaught and franklin just haven't shown they are on teh same level atm... onslaught especially
__________________ Quotes from Hia8:
"I claimed that the science is sometimes faulty."
"You don't understand. This is fiction. That means none of this stuff really happened."
"There is no writer to purposely ignore a character's natural ability just because it suits the story."
"in some cases because the writer knows that Character A will dominate Character B easily and refuses to allow this to happen for the sake of the story."