Hi @MarcoLazzarotto
I don't know if there is an ADE-OS CLI command to list the admin users (at least, not in ISE as far as I can see).
If the admin access is AD enabled, then (if you know which AD group this is) you could consider also disabling those accounts (or removing them from the ACS Admin AD group).
Your best bet might be to get a Flash enabled browser solution to manage that box (there are folks on the web who have solutions to bypass the Adobe killswitch and run this on an older standalone browser)- and then to consider migrating off of ACS onto something else.