When somebody feeds intentionally
When somebody on your team or the enemies team is feeding intentionally (And I don't mean 'having a bad game' I mean running down mid and standing still so the opposing team can easily take them out) REPORT them. Nobody wants someone like that on their team, it makes the game more difficult for you, gives the opposing team an advantage and is very immature. What is just as bad however, is killing said player multiple times and then not only refusing to report them, but HONOURING them. You honour an opponent for being gracious, fun to play against, and not being toxic. Not for feeding you numerous kills.
Please, when you are in a game against one who is intentionally feeding, think what it would be like if they were on your team and report them.
Also, don't report people for feeding because they're merely playing poorly, everyone can have off-games and you shouldn't be aggressive towards those who are having a tough time. Help them out and you're more likely to win.