Less reward for clean up kills

They didn't help kill they just picked off the scraps. With the exception of maybe ults like jinx or Garen which are meant to executes or global ults, clean up kills could only give half gold and xp since the person did not actually help to fight.

You could make this work by having a system that will limit the ill reward when the %hp is less that 5-10% or so and the killer did not deal any damage before it got that low.

I get frustrated when I dominate lane only to have another lane let my opponent clean up. This is annoying because it rewards champions who would have lost lane (or at least had difficulty pressing their opponent) still be a threat and it punishes the player who actually chose to counter them in the first place because they might not be able to keep up with just farm and roaming of there own. (This might also stem from my somewhat bias mentality that lanes who picked counters should win more than they should lose if 1v1 if the player's skill levels were equal).

For example: vs Malz normally beats Yasuo in mid lane 1v1, but yasuo can easily clean up other lanes to stay even. Since Malz has poor ability to take towers if he does not have an army of voidlings or it is early game. Even late game his ability to take towers is average at best. Yasuo can easily fell a tower at all points of the game unless he is behind by a lot. Malz also struggles when roaming due to his low mobility, notable lane absence, and the need to be able to set up for the roam so he can be in position to ult. If Malz does roam, yes he could get a kill but he will lose lane almost guaranteed. He also need the farm. Yasuo has better mobility to roam with. Can turn fights even if he is their late, does not need to prep for his ult, and his w makes bot lane an easy lane to clean up.

So why not reduce the reward for clean up kills so that the person cant just always abandon their lane knowing it cant be pushed fast, take a few kills, and come back stronger than the lane opponent even though they were far behind.

Now I don't want to discourage roaming. I just want to make it less of an alternative to laning.

Remember this is all just thoughts and ideas. I am open to suggestions on what you think would be sufficient.