Flash could vibrate through sups and stop his heart.In what way? I can't see Flash taking on Superman in an all out brawl. Yes,there's a variety of things he can do with his speed, but Supes is pure power and durability. All Superman would have to do is land one solid punch on Flash and it's over.
That said, I'm far from a DC expert so if anybody has any comic receipts to disprove me then please share.