What character are you playing? It might also help to share what the Rash was doing or even use the Xbox one tools to record your replay and share it with us.
Some characters have anti-air that is very effective against Rash’s corner vortex while others require tight timing and better reads and a few basically can’t anti-air him at all.
Obviously great players will make you feel helpless in a lot of situations (that’s their job), but one of the things to keep in mind about Rash is sometimes the timings are a little bit tight - so don’t give up if you try something that should work and it doesn’t. It may just be a timing issue.