Floatzel has really high attack and speed
He also learns Aqua Jet which is a priority move
Swellow could also be a good revenge killer because of it's high speed and quick attack
You're going to need a fast Pokemon as a revenge killer
You could also use Purugly with Fake Out, Liepard also works here
My Revenge Killer is Tauros with it's Return for any type but Steel, Ghost, Rock
I found these the best of all the fast NU Pokemon