I'm assuming that Special moves are your Hadokens, Shoryukens, Tatsumaki Senpukyakus, etc., while Super moves are the more cinematic ones.
Job 4:
Superman specials:
-Heat Vision (a sweeping eye beam that travels across the ground, like in the Injustice games)
-Super Breath (freezes the opponent, like the powered-up version in the Injustice games)
-a flying punch that launches Superman across the screen, giving him an option for mobility)
Iron Man specials:
-Unibeam (like in Marvel vs. Capcom)
-Jet Uppercut (an anti-air similar to a Shoryuken)
-Laser Cascade (uses a spinning laser attack similar to Iron Man 2, though with shorter range, as a "get off me" tool)
Job 5: MCU/DCEU characters
Black Panther:
To say that the MCU version of the Black Panther made an impact is an understatement. While he tragically might not be as prominent going forward, his legacy will live on in the MCU, and I feel like he definitely needs to be in this at some point. Marvel vs. Capcom Infinite gives a template, though so much more can be done with the character - Vibranium daggers, a counter move where his suit absorbs energy from enemy attacks, etc.
Shazam
Also known as Captain Marvel (if the game has interactions at the start of matches, maybe there could be a reference to that), Shazam is a mix of the awesome power of Superman and the wish-fulfillment of Robin - a young boy named Billy Batson who transforms into a grown man with the power of various gods and mythological figures (and King Solomon) when he says "Shazam". He proved to be so popular that DC sued Fawcett Publications for ripping off Superman - there were plenty of imitators, but Captain Marvel was the only one that was outselling the original. The Shazam movie is a bright spot in the DCEU - light-hearted and funny, it proved to be a success for that cinematic universe. (shame that Henry Cavill couldn't actually make a cameo in it)