Fundamentally game breaking damage bug

If I am a 6 item full ad Graves at full health (Infinity, Phantom, Deaths Dance etc) and I shoot a squishy Jhin twice who does not have any bloodthirster shield and only resist item is a guardian angel for 30 armour which of these outcomes will occur

a) he dies (logical) b) I chunk him heavily (also logical) c) I do absolutely no damage and one non 4th shot auto from him heals him for more damage than I did with only bloodthirster as a lifesteal item d) I jump off a cliff because fk me guess what, option c) occured

What a wacky world

Edit: Here are some screenshots, you can see in the second Jhin has lost a tiny amount of health, maybe like 30. That is after my shot and before Jhin's lifesteal auto kicks in (when his lifeseal does hit, it overheals him a bit and my 2nd auto doesnt get through the teensy shield) My friend also mentioned Threshs Knights vow but the small percentage redirect doesnt reallocate nearly enough to make those 2 autos so weak.

https://i.imgur.com/LrT0Ehg.png https://i.imgur.com/soQLRk7.png