superadmin and admin access on a server, whether or not you are running ULX or not, have powers that must be held in utmost trust.
If you're running ULX and a group inherits from admin, or a custom group has access to ulx rcon, ulx banid, and several other 'trusted only' permissions, there's no easy way to prevent what you describe.
DarkRP may also give permissions we have no control over.
Best advice - Don't give so many keys to the kingdom.