Overpower would be kinda stupid without all the characters we've come to know and put on outlandish teams together. Anyway, here are my picks for the Top Five characters in Marvel Overpower.
I Holocaust - Holocaust has the best specials in the game. He has an 8 Any-power attack, an avoid 1 attack and a negates 1 special. What I like about Holocaust are his ratings, not beacause they're high but beacause they're not spread out. Just stick Holocaust with comebody like Thor and you've got the start of a good deck.
II Silver Surfer - Silver Britches comes in a close second. Huge ratings and defensive specials out the yin-yang make the Surfer a good teammate for just about anyone.
III Mr. Sinister - With three killer One-Per-Decks, the avoid 1 attack and the 8 Intellect, Sinister is a good person to round out any deck that has a 6 or 7 Intellect and some rating space.
IV Super Skrull - I was surprised when I really looked at Super Skrull for this list. Good ratings, the Fantastic Enemy special, and some good, yet common, One-Per-Decks make Super Skrull a good choice.
V Iron Man - His overall specials could be better but still, never a bad choice for any deck.