Originally Posted by
Mirage
Let's see here. Is it possible to defeat something which is invincible?
Did you defeat Zeromus?
In order to be invincible, something or someone must be impossible to defeat by anything in the entire universe. The crystal (and Cecil's spirit, whatever) weakens Zeromus. The fact that Zeromus is weakened is irrefutable proof that he is not invincible. Had he been invincible, no one would have been able to weaken, and then defeat him.
If there exists anything, no matter what it is, that can defeat someone, that someone is not invincible. Practically impossible to defeat by the majority of the creatures in the universe, sure, but that doesn't equal invincible, just pretty damned near it. :p