He was actually pretty damn fast and agile in that movie, and quite skilled with his weapons and shield as well (that wrist energy shield and those boots were pretty sweet). I would say that he could take the vast majority of street level guys in the MCU, but would lose to anyone around IM level or higher. I actually immediately thought Star Lord when I saw him in action for the first time.
Depends what his energy gun does to ironmans armor, we know ironmans armor is susceptible to heat damage..
With gun, he gets to ironman level...well...Hawkeye could nail him with an arrow for sure, he was nailing chutari on the zip, explosive arrow might do some serious damage and going by feats, he's yet to miss a target...
Minus flight but with gun, i think Cap would take him. Even close range WS had three guns two of them fully auto and couldnt nail Cap. Flight would give Caine the obvious edge as he could take pot shots on the go and out of reach.
Straight hand to hand i think Widow drops him 6/10.