i dont who it is but i know who its not:
Cap: i agree too obvious
Wasp: IDk it looked like man hands, and she's too needy and vulnerable right now to be diabolical
fury: could be, he ususally calls ppl soldier
black widow: IDK she would have brought out her armor, but she is a spy after all
IM: too busy having fun with widow's vagina
also it could be pym, mad as shit for fury rejecting him joing up back as ant man or his free ultron droids, he was offereing to thier service.
since pym made sure that hulk didnt die, it could be hulk mad as shit that they tried to execute him, and lied to him that he was exhonerated before they drugged him.lastly it could be loki disguised as one of the heroe's to tear the team apart.
with regard to the thor battle tho i think that scientist guy(loki) said that it was designed to make the wearer the most powerful superhuman in the world. so in 616 term it would be thor's tradiational belt of might, or whatever fancy name he had for it.