Reminder: King Arthur has functional immortality, that can only be broken by all the Sacred Swords being in one place.

There is only one way to ACTUALLY kill Arthur.

Put the Sacred Swords together and beat him up.

So basically what the post above me said.

Infinite,all those guys never even beaten sonic,like,mephiles,doing a cheat attack in the back does not count

Tough answer.

@CyberSonic6096324.0 True, but so is Mephiles, which doesn't seem to be able to be broken by anything natural.