So after starting a new game today a player chose to use Karnon due to his hero ability. "Each time a monster attacks you, after rolling dice, you may suffer one stamina to cancel one surge rolled on the attack". Now here is where the problem lies. I take this as you can only cancel one surge with one stamina per attack. Where as the player feels that if he has three stamina he can cancel three surges on the same attack. Any suggestions or helpful info for this? Thanks for your time.

I suppose it could go either way, but I'm pretty sure it's just one stamina for one surge, period. Given how much less frequently surges appear in 2E, allowing more than one at a time seems unfair.

Based on the "each time" I would agree that it can only be used once. Next time you are attacked you can use it again.