Flash Villains Vs X-Men Villains

Cicada

Peek-a-Boo

Mirror Master

Gorilla Grodd

Abra Kadabra

Kilg%re

Replicant

Vs

Mr. Sinister

Nimrod

Sabretooth

Magneto

Sugar Man

Holocaust

Sebastian Shaw

Yikes, you got some obscure ones there on the Flash side!

Yeah, I like the OBSCURE ones more than the mainstream ones. Plus, once you start counting the mainstream ones, it gets a little lopsided. Savatar, Zoom, Professor Zoom, Inertia etc...

There's also ones like Tarpit and Shrapnel, Dr. Alchemy, Trickster (new or old), Captain Cold, Heat Wave, and other Rogues like those.