Frank VS ken Shamrock would have been awesome if the fight was both of them in their prime. Ken is too old now and has no chin and if ken and frank fought it would be pathetic. Hoverer when these two were in their prime the were the top of the food chain.
If they both fought in their prime i would say ken would have won. He was bigger and stronger. Also when you look at a common opponent in Bas ken beat him twice one in total domination getting him in a knee bar in 1:17 in the first while frank lost twice.
Ken and frank are on the GOAT list imo and i would have loved to have seen them fight in their prime.
"The fat man flies at midnight"