How to beat lethality Quinn. Quick guide
Play a mage, build zhonyas, tabi boots and liandry, afterwards go for frozen heart, deadmans plate and thornmail.
https://i.gyazo.com/39c2353006727e2c08396592f8d5b2f8.png
The only way you die is if you get focused down by the enemies that deal ap, as you will have 390 armor but no mr. Seems like this is the only way right now.