After testing it rather thoroughly me and my friend Angrir found that if Blitzcrank pulls Quinn into a bush and she uses Vault on him right away she would instantly kill him. Testing further we found that it also happens when Blitzcrank pulls Quinn out of the fog of war. She will kill him instantly if they are in the same bush. However the bug doesn't happen if they are both visible in a lane it must be in the fog of war or bush.

Further testing showed that it doesn't instantly kill him but it does around 3000 damage to him at all levels regardless of what Quinn's build is, Tested by stacking warmogs on Blitzcrank with 5600 Health, Vault left Blitzcrank with around 2600 health.

Reading through the forum there was a bug post mentioning that Vault would instantly kill Lee Sin but they couldn't replicate the bug and i believe this is the same bug happening.

Tested with Leona, Darius, Diana and Thresh pulls but couldn't replicate the bug.

Nice catch :P

Intended, it adds an interesting element of counterplay.

Boot to the Head style is a powerful martial art...

But yeah, that seems to be a major bug.

working as intended, i hate that robot >_>

Please don't fix this.

When shyvana jumps if you e at the right time as quinn you instakill her as well.