If someone destroyed the planet, the Flash is on, he would run around and revert the time. Then before his opponent had the chance to get that far, he would eat trillion trillion infinite mass punch sandwiches in one femtosecond, while being unable to move due to having not kinetic energy left with all that while lacking half of the body, since it's sealed in the speed force.
At the same time bazillion crapillion of rocks would come flying at the opponent, all loaded with kinetic energy just to explode on contact oh and they would be intangible of course so that you couldn't prevent that from happening. Not like there would be any need for it, since you still wouldn't be able to move.
IT'S SPEED FORCE, *****!
I would actually like to see a Thanos VS Pre New 52 Flash thread and if the Thanos fanboys on this board would actually argue for Thanos.
And of course that's not an official Flash drawing. It's a troll by a genius, who came up with that nonsense and made the Flash look like a 'turd to fit DC's style of writing more.