Hm, my colonists seem to stop fighting when one of them gets downed or they both beat each other enough but never to the death.
Now if a colonist went berserk I would understand since they don't shy from using their weapon in that case. If you are talking about going berserk its best to force the pawn thats close to breaking to drop his/her weapon so its only fists for them and to make those that you send to subdue them drop their weapons as well.
But as I said, social fights never resulted in fatalities in any of my games, scratched eyes and broken bones yes but nothing more.
Now if a colonist went berserk I would understand since they don't shy from using their weapon in that case. If you are talking about going berserk its best to force the pawn thats close to breaking to drop his/her weapon so its only fists for them and to make those that you send to subdue them drop their weapons as well.
But as I said, social fights never resulted in fatalities in any of my games, scratched eyes and broken bones yes but nothing more.