Now for me this would be won by Black Widow mainly because she is a master assassin. Yes i know Bruce has dealt with Rag Al Ghul and other assassins but she is from Russia, she is beautiful and powerful so she could seduce him then kill him. But if Bruce was smart enough to realise what was happening (which he is, DUH he is Batman) then it would be a fist fight. I personally think that Natasha would win in this case mainly because of how tough, determined and agile she is.

Please say if u agree or disagree and why.
~~~ Black Widow