Jay-walking.
Jay-walking.
Killing Robin, Alfred, or any member of the family really.
Eating all of the Crackling Oat Bran
Grave-robbing his parents' graves, Sleeping with Alfred/Dick, Selling his secrets to the highest bidder, killing another hero
I think Bruce wouldn't be able to forgive Selina if she purposely did something fatal to Damian or killed somebody out of fun/spite.
I think those two things he probably wouldn't be able to forgive her for. But then again, he knows most likely she wouldn't do those things either.
It's already been said but if selina murdered someone in cold blood or murdered someone (who probably deserves it because this is selina we're talking about) but bruce feels like murdered wasn't necessary she could have kept the person alive. Killing/purposefully harming his family goes without saying.