Sam or Dean?
Dean, for sure. The only time I can remember Sam actually beating Dean in an all-out brawl he was either A: high on super-powered demon blood or B: Soulless and uncaring what happened to Dean
or himself.
Crowley or Bobby?
Crowley. I mean, he's a demon and the King of Hell, Bobby's... he's awesome but in a bar brawl? No way.
Castiel or Jack?
Jack because Castiel would never seriously harm his 'child'.
Mary or Ellen?
Ooh, now that's a good one. Both well-trained, though if you go back to Ellen's S2 introduction, we learn that her husband was the hunter, not her. Something tells me that
Mary is better trained and grew up more steeped in the hunter's life, giving her a slight edge on Mrs. Harvelle.
Rowena or Bela?
Rowena is for sure the winner, with her immense power, but I
do think that Bela is conniving enough to give the redhead a bit of a run for her money before she won.
Kevin or Charlie?
Charlie, again this one seems the obvious winner. She's a tough one and has probably been in a few bar fights in her time already, whereas Kevin has been mostly sheltered and wasn't built for the life that chose him in canon.
Edit: Noticed only now the no-powers, pure brawn, but most of my list still counts I think
Here is my list:
Rowena or Abbadon?
Ruby or Anael (basically Jared's wife or Jensen's wife

)?
Bobby or John Winchester?
Jody or Donna?