Doctor Fate Vs. Nightmare

 

I think the plan is still for a third Dr. Strange movie to be made.  Nightmare would be a great candidate for a villain.  I can imagine a lot of cool dreamscapes and scenarios with him in the mix and it would be fun to see them realized.

Justice League of America and Gargoyle

 

There has been lots of discussion about what to do with the next Avengers movie now that Jonathan Majors' Kang is out of the picture.  They could recast and call it a variant, but Marvel seems to want to move on.  Many have said to use Doctor Doom, but he should be with the Fantastic Four.  I'd love to see Nightmare finally make a live action appearance, he certainly has enough power to become a franchise wide threat.  Plus, Ironheart, which was to debut Mephisto, has been shelved indefinitely, so there's an opening for a mystical adversary.

Challengers of the Unknown Vs. The Hulk

 

Pavement sure had some strange properties in the comics I read as a kid.  Characters like The Hulk, Superman and The Thing would often pull stunts like the one above, whipping a sidewalk like it was a towel.  Another move was to roll the street up and wrap your opponents in it.  These were always visually impressive displays, if not always scientifically sound.