when you make someone a superadmin just type 1 for teh immunity flag..
ulx adduser blahblah superadmin 1
>> (Admin) has added blahblah to group superadmin with immunity
This will give them immunity to all commands against them from everyone.. except other superadmins.. this is because superadmins have immunityoverride. Which COULD be removed from the groups.txt.. or on an individual basis with ulx userdeny <user> "overcomeimmunity"