Hello!
Sometimes players kill teammates on purpose, just for fun. And victim can't do anything about it. Best hope for revenge is try to kill him after spawn. But that freak can actually think that it is funny so he will focus on you entirely. If he has friends they will hunt you too. So you end up dead in first few second after spawn.
You game session is completely ruined! (True story...)

As a solution I suggest enable players to punish team killers. After FF resulted in death victim will see menu with options. For example:

  1. forgive
  2. kill
  3. kill and make him skip (1-3) next respawn

That is "must have" options. Also it will be usefull to add another "soft" punishments, like put a beacon on him, take all his weapons except handgun, slow him down...