Kuuga and Agito can handle Captain America by themselves. Probably Kuuga in his Rising can do solo.
Ryuki can handle both Hawkeye/Ronin and Black Widow provided he has some reflective/mirrors around. His fighting style isn't really graceful as the two.
Kabuto can beat quicksilver no problem and him and Faiz can fend off Scarlet witch provided both are aware of her mind abilities/Kabuto using clock-up to end her.
Armed Hibiki, King form Blade, Den-O climax can probably fend off Black Panther. I still don't know if T'challa's suit can take a hit from any of their attacks.
Kiva can beat Winter Soldier.
Decade and ZI-O can handle Iron-Man. If there's a sign that they're losing, ZI-O II can reverse time. They say Iron-Man's "super power" is to adapt quickly into any situation, but Decade and ZI-O's constant kamen rides and armor times can confuse the armored hero.
OOO and W against Shuri and Okoye (+her Dora army?). Hell, OOO enough can end a civil war in vietnam. W can also tap into Gaia Library to get an edge in thefight.
Fourze against War Machine. Fourze has the necessary tools to wear down War Machine unless he decided to use Cosmic early in which case the battle ends early. Although he'd probably convince everyone to befriend the avengers.
Wizard, Gaim, and Ghost all combined against Dr. Strange. Strange probably can't soul punch Takeru's soul out of his body if he's already dead, Kouta's Man of the beginning powers and Wizard Infinity should hold their own.
Drive and Ex-aid to counter Hulk. Muteki Ex-Aid could tank the Hulk and Drive in his Type Tridoron could chip away at the Hulk till he goes down.
I can't prove if Build can beat Thor even though Build has fought against planet-destroying-level of aliens but maybe with the help of Kuuga and Blade should be good.
Decade using the neo decadriver can beat Captain Marvel so long as Decade doesn't energy-based attacks.
--
Even with all these, I'm not pretty confident the Kamen Riders can win. Maybe a tie if Blade dies and it ends the world or Kuuga managed to land a kick in his ultimate form that breaks the world.