It's a hard problem to solve and I think there is no one fix all solution, it was already discussed somewhere on Nostr github. My thoughts are that the user could choose revoke methods and relays that implement them, one method could be using something you own let's say a bitcoin address, that you would publicly put on your profile as a revoke mechanism, then you would send a tx to the relay address from your btc address would be proof that your account is revoked. Another way could be you set npubs for social recovery.