Hitman Champion

We all know it. Assassins are basically Hitman. So why don't we have a Champion who has a passive that benefits him when killing a certain champion? Let's see a good example hmm. When he/she kills ________ he will gain _________ He will have the champions picture somewhere on the screen so he can clearly see and also the Summoner name. I don't know what I am saying. But a hitman in Piltover or Zaun doesn't even break the Lore. SO WHY IS THERE NOT A HITMAN CHAMPION YET? We all want it.