In City of Heroes, you didn't kill your targets, you *defeated* them. After they were down for the count, teleporters would (eventually) automatically take them to jail.
Of course, some heroes defeated their targets by sticking swords and claws RIGHT THROUGH THEM, or shooting them with assault rifles, but those bad guys are tough, they can take it.
I guess that they didn't feel like bothering with a similar concept for CO.