15/3/3 as rengar and still lost

reason is even though you did good as rengar assuming you were jungle you starved your lanes of kills and probably did not fight for a reason, every fight past 7 minutes should be for a purpose, weather it's dragon, taking a tower, or even forcing mid game faster. when you teamfight for no reason and don't take objectives you lose. Think of it like shaco, if you take all the kills from ganks you'd better be soloing that dragon at level 6

This is a team game <3

first thing : Lv 14 lol second: If you're good at rengar then you can just 1v5. Especially in plat I've done it before. third: Make sure you have the right items and are focusing targets in the correct order. fourth: Once you have this stuff down you just need to use bushes and fog of war right as well as dodging skill shots. fifth: try to use your useless teammates as meat shields or bait. It'll make things a lot easier. Hope this helped :D