Deadman vs. Mysterio. I think they'd match up quite interestingly.
Unless that Slade is able to come with a great strategy to bank on Kaine weakness, he is doomed, Kaine is way faster and stronger than him.Deathstroke vs. Scarlet Spider (Kaine Parker) --- would be a more even fight than Deathstroke vs. Spider-Man, since Kaine has the killer instinct, albeit constantly repressed due to his efforts to be more of a hero in the mold of his brothers Peter Parker and (pre-Clone Conspiracy) Ben Reilly, that Peter lacks, along with (most of) the physical stats to match Slade.
"Wow. You made Spider-Man sad, congratulations. I stabbed The Hulk last week"
Wolverine, Venom Annual # 1 (2018)
Nobody does it better by Jeff Loveness
"I am Thou, Thou Art I"
Persona
Clayface vs Black Panther
Despero vs Captain Marvel
Klarion the Witch Boy vs Wiccan
Captain Nazi vs Captain America
Amazo vs Iron Man
Solomon Grundy vs Dr. Strange
I think a better matchup would be Black Panther versus Red Lion. Red Lion is the answer to the question "What if Christopher Priest wrote a Black Panther that D.N.G.A.F https://dc.fandom.com/wiki/Matthew_Bland_(Prime_Earth)
"The Marvel EIC Chair has a certain curse that goes along with it: it tends to drive people insane, and ultimately, out of the business altogether. It is the notorious last stop for many staffers, as once you've sat in The Big Chair, your pariah status is usually locked in." Christopher Priest
Most of the Bat-villains against Spider-Man and Daredevil.
the x-men stay in krakoa,put their phones on ignore, everyone goes to the tiki bar to watch the live of the enourmous beatdown the justice league lays, multiple drinking/snack games ensue each time the avengers eat the dirt.
Joker vs Punisher.
Kaine's weakness, such as it is, is that he can be (and was) pretty scummy sometimes, but he's nowhere near as scummy as Slade can be, as he's at least ashamed of his scummier past behavior and has put forth genuine effort toward being a better person.
Black Panther vs. Red Lion? I could see that, especially if Christopher Priest himself wrote it.
The spider is always on the hunt.
I always thought that his weakness was his temper and his self-loathing (he really was down on himself in the last strecth of his solo), still Slade would need to use some elaborated big scheme to put Kaine against, a phisycal confrontation would just go.bad for him.
"Wow. You made Spider-Man sad, congratulations. I stabbed The Hulk last week"
Wolverine, Venom Annual # 1 (2018)
Nobody does it better by Jeff Loveness
"I am Thou, Thou Art I"
Persona
Good take on Kaine's weakness being his comparative lack of self-control when it comes to his temper and his self-loathing. I could see Slade trying to play on Kaine's temper if he had time to study him more closely, but as for an all-out physical confrontation, depends on what suit he's wearing. The Nth-metal suit, as far as I can recall, further augments his physical abilities to a certain degree, while the Ikon Suit absorbs kinetic energy directed at it similarly to Black Panther's more recent suit, so he can probably withstand at least some of Kaine's blows, if it can survive a hit from Superman.
The spider is always on the hunt.
A mini with Daredevil vs Ra's Al Ghul. (and the league of assassins). Could make for compelling drama. I doubt that Ra's would see Matt as a potential heir. Or would he?
Reign vs Captain Marvel
Solomon Grundy vs The Incredible Hulk
Lex Luthor vs Iron Man (Lex gets to wear his Lexo-Suit)
Bane vs Captain America.
Scarecrow vs Spider-Man
Mr. Freeze or Killer Frost vs the Human Torch