I made a bunch of decks and tried them each for about 5 solo games or so against Basic difficulty villains.
My most successful solo decks:
Iron Man / Leadership : Allies keep Iron Man alive and the threat down while Tony assembles his suit. Three suit pieces is usually enough to start living in Iron Man mode. Second Rocket Boots can be recycled with Stark Industries for continuous Aerial trait. I never came close to losing, even with 4 schemes out at one point, because Mark V Helmet is ridiculous.
Captain Marvel / Justice : Justice role completely smothers threat and gives Carol time to set up gigantic death rays from outer space. There are a lot of energy icons in the Justice role for that sweet, sweet synergy. As a side note, Justice might be equally as good for Iron Man to stall things out and to help him fire better lasers.
I will also note that both these decks cycled themselves nearly every game.
My least successful solo decks:
She Hulk / Aggression : Some of She Hulk's cards are definitely more for group play (Ground Slam) and some of the Aggression cards are really bad in solo. Like if you, for example, never draw a minion. She Hulk wants to switch between Hero/Alter Ego as often as possible. Sometimes she found herself racing the threat clock but her aggression cards and Gamma Slam just wrecked everything before it was too late. Still, there were so many blank cards for solo
Black Panther / Protection : This seemed like a no-brainer because of retaliate, but it was pretty bad. Black Panther has very few ways of naturally reducing threat. Of course, grabbing Tactical Genius immediately mitigates that somewhat. I also had an issue with card costs and awkward hands playing Black Panther. I lost several games because this hero/aspect combination is racing threat and can't always win. This is probably a better match for multi player.
I honestly think the issue is more with the aspect and not with the hero. Justice and Leadership just seem more suited to solo play, where being in Alter Ego form during the villain phase can just immediately cost the game from zero threat with a regular scheme and then an encounter card scheme. In solo, heroes want to be able to live in their heroic form to avoid this or have Justice cards to hard counter it.
Did I get something wrong? Thoughts/advice welcome.