20He was never fired
Michael Scott proudly displays his “World’s Best Boss” mug on his desk. While he has his redeeming and charming moments, it is clear from episode 1 that Michael is far from the best manager the world has to offer.
Michael proves himself to be a menace to his coworkers
time and time again.
Arguably his most ruthless offense came when he tried to frame Toby by placing a bag of a certain (what he thought was) illicit substance in his desk.
It turned out that Michael himself got tricked as the bag was filled with Caprese salad, but nonetheless, the intent was there.
He has many other moments similar to this, but this one stands out because the intent was to get someone canned. It is surpsing that as a result, he did not get the boot himself.