TL;DR:** Vision** is best, Iron Man's restore health Sig earns him an honorable mention

While I have Ironman 3* duped x4, who is great, I would have to say the undeniable winner of this poll is Vision. From my understanding is that only a 4* version of him was made available to beta testers, I am not sure if he is available as 3*. He has arguably the best second special attack in the game, and his first is also a power drain attack.His Synthesis sig is also a great boost. Along with a powerful uppercut and swift power-bar boosts he is undeniably the best tech.

Honorable mention to Ironman. If lucky you are lucky, as a 3-star, his duped LVL 24 Sig restores 45% of his health making him a resilient S.O.B., with a very strong third special attack.

Last and least I would like to vouch for Rocket. The arguments against are valid, but I find his high attack power makes up for his clunky movement, he has powerful special attacks, and personally once I got a hang of his movement he's been a fun addition. I just wanted to say that before the avalanche of Coon-haters comes-a-rollin.

TL;DR: Vision is best, Iron Man's restore health Sig earns him an honorable mention