The problem is not the death count. I can die even 20x times to save my carry, as it is my job as support. He can die 6 or 7 times as he could have a tough lane match-up, a lot of jungle pressure, or just being defeated by some lucky crits on a tight fight or being dived under tower with the result of a 1 vs 1 swap, and I can see if he deserve my help even if behind
The problem is when you see that you and your ADC aren't on the same boat about what to do OR when you see that he can even been mechanically good but fail to grasp a pair of things about the way the game is going and the way to exploit to the enemy team or adapt to it
I was playing with a friend of mine that kinda mains ADC, and he was doing fine as far as lathitting goes. The probelm is that with Jinx vs a Vayne in the lane to get every single CS correctly without losing even 1 of them, he let Vayne pushing at early levels and we were often fored to play under tower. The few times we could actually push them back a bit and gain the center of the tower, I warded river brush, and was waiting in the 2nd bot lane brush(looking from purple side) to set up something as Alistair to engage. He stopped at the edge of the first brush and did not move waiting for the minion wave. Their jungler(Jarvan, in another game it happened the same thing and was Lee) with their gapcloser came from the river and gapclosed to him in that brush. I and the enemy bot lane went through the point, I succesfull Qed one time 2 and one time 3 of them, exhausted the closest enemy but he however died...and then he got angry because I didn't exhausted the ADC(which would have required to move away from him anyway i exhausted the jungler or the support I don't remember) when he was yet down at about 1/4 of his health and was basically dead if not flashing away during Q knockup time. This happened 2 or 3 times in the same game. Not need to be said that we flamed each other, we sucked hard and we lost the game beause their bot lane carried hard them
I can't say that he is a bad player mechanically, he is probably considerably better than me. But as far as understanding how the game went, he was doing everything wrong. Not pushing a vayne under tower at the cost of some CS(given that she can't farm really well under tower early) is non-sense. Use multiple times Q to clean lane while standing still for seconds doing nothing and not change with minigun make little sense for the way Jinx kit is built...even though he didn't lost 1 CS by doing it so but let Vayne outpush. Not using the E in advance looking at what was happening before, being engaged hard by their junglers in that brush, basically dying and then complain because Exhaust wasn't used that well(I admit it) not looking at the more important fact that I was able to Q all of them and give him a slight chance to save himself when he was fucked even if exhaust was used on the proper target show me that he hasn't understood how the game went. And this not being technically a bad player, or a worse player than me
