I lose so badly with McCree. So, so badly. My winrate is hovering around 40%, which is one of my worst-winrate heroes. I'm not entirely sure why, either, since my other stats are decent-to-good, especially since I've been practicing with him lately.
My winrate with him in comp. is positive (and my stats, including accuracy, are much better than QP in an admittedly small sample size), so I guess partly it's my use of him in solo queue QP, where things are silly and teams are uncoordinated. But it just feels like win-lose-lose, win-lose-lose. Also I used him quite a bit through the period where he was heavily nerfed.