Dealing with a bad support as an ADC

What can I do to mnimize the impact of a support thats really bad/trolling when I'm ADC? Sometimes I get supports that just die to every blitz or thresh hook, and I have no idea what to do to stop that from happening. Last game my thresh was missing every relic shield last hit, so I started trying to deny him them. He just started inting and competing with me for CS even if he didnt have targons stacks. If I had known he would do this, I suppose I could've let him miss 1 or 2 CS per wave, but then I'm still at a huge disadvantage. TL;DR It almost feels like an auto-lose for the ADC player when the support is really bad. What can I do, as ADC, to prevent this from happening?
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