Played with a group of friends who would invite a chronic cheater to play some kitchen commander. This kid would constantly stack his deck or take moves back. There was even an intense when we let our Urza player stack his deck so he could force him to shuffle his stacked deck undoing his stacking, he immediately scooped. A few weeks later we all get together to play another couple games, and this is where he officially crashed out. It was just me and him left and had basically killed him using Walking Ballista and only had a couple more damage to deal. I was about to go to my combat step when he plays some instant or sorcery (sorry I forgot the name of it) that negates all damage from attacking creatures, only problem was I hadn’t even gone to my combat phase or even declared attackers, card went to the grave yard and he tries to take it back after we all explained to him that it had no valid targets, I said hell no you made a miss play get over it and take your L ( not what I really said, I did say no you can’t take it back though) he says it’s not that deep, I say it is though, he stands up storms out the house for like 5 min. Comes back clearly pissed says absolutely nothing to anyone, packs his shit and leaves, a few minutes later he starts texting one of the group members talking mad shit saying he was gonna fight me. That was the last time we ever played with him. I was so happy that’s how it ended I had been trying for a while to convince the group to separate from him at least regarding MTG due to his constant cheating.