some RPs use die rolls. Not sure how they go about making it fair, but it can probably be used well.
Still, there are many ways to deal with it. Best way is to have it be balanced. Each side affected both taking and giving some hits. Whenever a player isn't being fair about it, the GM should step in. Either by instructing said player to not be as overpowered in behavior, or by forcing it to take some hits. We feel it is only in extreme circumstances that the GM should step in with a kill order.