Comprehensive list of all Kai'Sa nerfs:
8.6 - W AP Ratio reduced from 65% to 45%
8.6 (Hotfix) - Base AD reduced from 65 to 63
Mana Cost increased from 45 to 55
8.8 - Base Health Regeneration reduced from 6.2 to 5.5
Health Regeneration Growth reduced from 0.75 to 0.55
Q Bonus AD Ratio reduced from 40% to 30%
8.9 - Q Upgraded Missiles Fired reduced from 12 to 10
Missile Damage flagged as AoE in all cases (counting this as a nerf since AoE gains reduced effects from certain spells effects)
E Bonus Attack Speed Duration reduced from 5 seconds to 4
Runaan's Hurricane bolts no longer grant E's cooldown reduction
8.10 - Base Armor reduced from 33.04 to 28
Base Health Regeneration reduced from 5.5 to 3.5
Base AD reduced from 63 to 59
8.11 (Hotfix) - Passive Plasma Base Damage changed from 7 - 12 (based on level) to 4 - 10 (based on level)
Passive Plasma Per-Stack Base Damage reduced from 1 - 9 (based on level) to 1 - 5 (based on level)
Passive Plasma AP Ratio reduced from 20% - 40% (based on Plasma stacks) to 10% - 20% (based on level)
https://imgur.com/a/atmYjOu