When it comes to running servers, admin activity is key. If you control your servers properly you should be able to seize a lot of issues in their tracks as they occur. The way I deal with team killers is I tp them to a remote location, run "player allowDamage false;" locally and tp myself to him. Then we have a nice little discussion. If they are out to troll they will avoid you and respawn or disconnect from the server. In that case I give them one more chance, until I kick them. If they return and continue the behavior then they get a day ban.