I am an admin of a channel but cannot remove deleted account from admins as well as other admins that the user promoted. Is there any way to do that?
As far as I know, your best bet is to contact the group owner as they are the only person who can remove any admin, even one appointed by someone else. The other admins can only remove those who they appointed themselves. If the one who appointed the admin and then deleted their account is the owner... Don't think anything can be done in that case.