How to nerf lee sin
MS lowered to 335 (he has multiple dashes and that's still decent MS)
Q CD increased by 5 seconds but using the secondary dash effect lowers its CD by 5 seconds (miss or hit wrong target to where you don't want to go in makes it a higher CD, otherwise it's a buff from better CDR effects when hitting your target)
W CD increased by 5 seconds if the shield is broken it reduces the CD by 5 seconds (similar to above effect with CDR but makes it weaker in escape)
R base damage reduced to 50/100/150 +2.0 total ad, causing the initial target to collide with an enemy champion causes him to take 50/100/150+1.0 total ad of the initial damage again and the target he collided with to be knocked up and take 100% of the initial damage
This buffs R to be 600 base damage and 6.0 total ad if you hit 4 other champions with your initial target
These changes are basically to make him stronger in skillful play, but one mistake is much more punishing due to longer CDs and lower base MS
It also prevents the ham assassination from an overtuned R which is only powerful when used right