I’m still exploring the game, but here are some of the assists I really like:
Thor B Mighty Smash - It can anti air and it creates ground bounce that is easy to combo off of. I usually have Dormammu on point and after I see Thor hit, I’ll do blackhole xxx chaotic flame.
Iron Man B Repulsor Blast - Big damage, controls space, anti airs and leads into easy combos.
Sentinel A Sentinel Force (Charge) - It’s been nerfed from MvC2, but even with it no longer functioning as a ghetto anti-air, it is still a really good lockdown tool.
Dante A Jam Session - Captain Corridor-like range, and it can lead into combos. What’s not to like?
Chun Li Y Lightning Legs - Really nice damage, high priority, and the hit confirm window is so large you can order a pizza, eat it, and come back and time to still tack an air combo on top of it.
Taskmaster Y Aim Master (Vertical) - It’s hard to avoid. It can anti air, pin down, or at the very least force your opponent to move. The only drawback is that he must be protected for a decent chunk of time.
There are of course more, like Dormammu’s Purification or Spiderman’s Webshot, that are decent. However, I’m looking for the best of the best here, so post up what you think the best assists are.