Hello, short intro: I just completed the 4-3-2 augment quests and tested out different builds, this is my take on the performance of builds.
Note: Blade of the ruined king % damage is overpowered here. first buy for yasuo 100%.
2Aug: Wandering, Tempest
Honorable mentions: Flicker, Growing, Infinity
build 1: Bork+2daggers--->finish rageblade--->phantom dancer--->black cleaver--> CDR boots--->any cdr u can afford. kindlegem/warhammer
Build 2: bork+attack speed boots --->phantom dancer--->infinity edge--> Bloodthirster/death's dance-->Dorans blade (dorans blade doesnt have nerfed lifesteal, unlike other lifesteal items. good last buy for remaining gold)
builds are not set in stone, you can mix it around and still perform well
Build 1 is anti kayn build. bork+rageblade to apply that high % damage, and CDR to spam ults to lock him down and make you temporarily invulnerable. this will cancel alot of his dashes and keep him locked in place for the entire team to deal damage. black cleaver armor shred.
Build 2 is for aoe damage with wandering+tempest. insane aoe damage, but low cdr and less lockdown for kayn with your ultimate
Team comp for 4-2 augs : Malphite+4 Yasuo. prefferably one with black cleaver.
Malphite augs: relentless+onslaught.
The idea is to use the malphite ult to knock as many mob into the wall, and use the yasuo ults to destroy everything. this is how you survive sticky situations and turn the tides of the battle.
During Kayn phase 3, if you get tons of mobs + kayn knocked into a wall by malphite, the yasuo's will probably end the fight if they press ulti within range. this is how you beat phase 3 with 2 and 3 augments.
there you have it. kayn fight depends on good malphite ultimates most of the time, so clear the roots for him, and have him look for those 3000 elo ultimates