It wouldn't happen in my company, but the Serbian law would also protect the employee enough that you'd need written proof about the behaviour, and the HR and legal team would have to review it to ensure we are not getting in trouble if we ever get sued for wrongful termination.

But even in the US part of the company, it should be hard for it to play out, but probably a lot easier: while most people, including other directors, seem to be good human beings, we are all stretched extremely thin and I am sure someone could easily get something to slip past us.

TBH, I am always surprised how do people get into situations like this and what are the types of people that do this? Like what do they gain from it? How far it takes them? I know I am naive and I have seen my fair of shit over ~20 years in the industry, but it still boggles my mind.

On the other side of it, I am sure one person — they under-performed but thought extremely high about themselves and got frustrated when I disagreed — would have claimed they were being mobbed by me (even after attempting to get improvements from them for 6+ months). So since you are not in your close-friend's shoes, do take note that they might not be sharing the full story and they are certainly not 100% objective either.

But for anyone having these sorts of disagreements with me, I advise reaching out to an HR or my superior directly with specific instances of problems they have concerns about or feel I am misrepresenting. For my part, I keep records of chats, emails and 1-1s to establish "facts" that drive any decisions I make, especially when it comes to life-affecting decisions like these.