Once had a manager who turned on me virtually overnight, to the bafflement of colleagues. I bore his constant attacks (including 'you were 10 seconds late this morning, I set my watch especially to check') until the day I could feel myself starting to crumble at my desk. I went to the ladies and fell apart and the dept sec sent me home and went to the manager and told him to back off or else.
I returned after a couple of hours of alarming sobbing and he called me in to his office. He was completely lost as to why I had had such a reaction (I was a bit shocked myself) and he kept well away for a while.
I had had a quiet word with HR about him after colleagues said they would back me up and as I was his only female staff member they told him he was on dodgy ground.
Eventually he left. The new manager gave me a lousy assessment 4 weeks after she started and I quit, refusing to sign it. My customers and reps asked me to stay, they asked her to make me, but we barely spoke during my notice. Walking out on the last day, wined and dined, laden with gifts and flowers, her final words to me were asking me to sign that flippin form.
Every job I've had there is one who feels the need to give you misery (and others) and I think half of them dont know they are a pain. For some it is the only way they can assert themselves.