Your favorite missing characters...

For villains, I’d say:

Red Skull
Kang
Zemo
Sabretooth
Super-Skrull
Klaw
Killmonger
Grandmaster (even if he is just an unplayable boss, I just want to see some Jeff Goldblum)
Ronan
Crossbones
Kilgrave/Purple Man

Also better versions of Magneto, Doom and Juggernaut.

And for heroes:

The rest of the runaways
Spider-Man 2099
Black Cat (I guess more antihero really)
Namor
Spider-Man Noir
Superior Doc Ock (or Spider-Man, whichever they’d prefer
Quentin Quire
Blink
Polaris
Mantis

and better versions of Storm, Beast, Colossus and Psylocke (the recently reintroduced Betsy Braddock one)

Im sure there are probably others, but that’s all I can really think of.

I can also think of about a thousand different costumes for characters I want too, like for example the astonishing x men version of cyclops, and versions of the fantastic four where the 4 logos actually all match ( they should all be wearing the same costume, so why can’t they actually all be wearing the same costume?)