If all reports of a manager complain to the managers manager, that manager will likely be reassigned or reprimanded in a similar manner to a manager and an IC.

Also I should note that in most of Europe (at least the parts I've worked in), a managers voice is just a louder voice in a room of other managers- and firing someone is something that is not done by an individual, it's a discussion with managers and HR.

It's not taken lightly to fire people, even in places that are "at will" (theoretically) like Denmark.