Well sorry to tell you this but nothing anyone can do besides report him at the end of the game.
but still again afking doesn't help the team any either...
actually when someone feeds like that their worth goes down so when they're 0/10 they're not worth a lot at that point..
The standard gain per kill is 300 gold. Every kill (in a row) by a champion increases their value (the reward gained for killing that champion) by 16.5%, up to a maximum of 500 gold. Each death (in a row) of a champion reduces its value, by 8.5% for the first death and 20% for every death afterwards, to a minimum of 50 gold. The bounty will reset to 300 if said champion kills an enemy champion
.
1st death: 300 gold
2nd death: 275 gold
3rd death: 220 gold
4th death: 176 gold
5th death: 141 gold
6th death: 112 gold
7th death: 90 gold
8th death: 72 gold
9th death: 58 gold
So a person going 12/12 actually feeds more gold than someone going 0/12...
The damage is done with them they're now worthless at 10 deaths.. those 4 more deaths were about as worth as killing a regular minion...
You just need to be able to have the power to fight them back.
problem is.. this resets when they achieve a kill
Every time you get a kill you're back at 300 gold again. consecutive kills raise this up to 500 gold shutdowns.
http://leagueoflegends.wikia.com/wiki/Kill
This is why Supports are amazing.. because assists don't count as kills so always focusing a support isn't always a good thing..