[DarkZtar]

If you have an advantage and think you can kill whoever is fed on their team, then go hunt them down and get the nice shutdown bonus for yourself~

Edit: And in general if you're ahead, it's generally not enough to just outright win your lane, roam around the map, pressure objectives with your advantage, roam to other lanes and win their lanes for them. If you're doing all this consistently the other team should find you sufficiently annoying to allocate significant time to shutting you down, relieving pressure on your teammates who /should/ use the time to catch up.