Certificate revocation
There are two cases to distinguish: The attacker issues the revokation or the owner issues the revokation.


Attacker revoking the cert. In this case the attacker has the private key and uses this to issue a revokation. He thus effectively takes any use out he could get out of theh certificate and the certificate is revoked as it should be in such a situation."Thank you attacker, you just did my job  without me having noticed the breach!"
Owner revoking the cert. The owner wants to prevent missuse of the cert and thus revokes it. This stops the attacker. Everything as it's supposed to be.