I've only encountered one violent RPG player. I've twice encountered table-flipper boardgamers.
He was a toxic player - I'd tossed him from one game for PVP... which everyone else but the target let me know he was trying to arrange... and they all colluded to prevent, in character, his plan. He threw a fit, I told him to leave. He did.
Later, I was running a GURPS game, and he asked for a second shot... i let him in. Campaign conceit required certain disads. He submitted a character which had them. I took a photocopy of approved. then, the following week, he acted against the required disad, I asked for the roll, he refused, claimed no such was on his sheet (indeed, it wasn't, since he deleted the required disads from it. Confronted with the photocopy, he got pissy. So I had the patron he'd removed (a 500 pt NPC vampire/wizard) soul jar him and destroy his body.
Player left. In a huff. Slamming the door after opening it violently into another player.
A couple years later, he stops by to see my roommate, notes I'm in the middle of a boardgame, flips the table. Roommate tells him to leave.
He was, for a while, a corrections officer. He didn't last as one - don't know if he quit, was fired, or was delicensed, but he later was working for parks and rec. I've not seen him since.
One of his friends, however, flipped his own table after losing badly at Advanced Civ... his own table, his own set. He and a smarmy other player had decided to collude to win... and everyone else figured it out. So they wound up taking the worst of all the calamities. They both wound up bouncing twice in a row due to no cities. Mr. Smarmy openly laughed when he realized they'd been caught and whomped... but the host? He was so pissed he flipped a heavy 5x8 foot dining table... three of us were 1 space from end of AST... and Mr Smarmy laughed even more... the host told us to leave, so we all, except mr smarmy, grabbed our sheets, left the property, and compared point totals...
then left. Never RPd with either of them. Mr. Smarmy later flipped my roommate's table... another "wasn't invited" wander in.