I've come to realize that if you're failing as Blue Kayn, it's not the form's fault... it's yours.
The form is actually telling you something. There's a reason why it goes by what you've been doing all game. If you're fighting bruisers all game and you're deep in fights and you're going in and keeping up the frontline, then it's going to go for red. Cause that's what it is. It deals damage, but it also has staying power and sustain along with engage with knockups.
But unless you're ridiculously fed out of your mind, you're not gonna assassinate that Tristana with it. You'll do damage of course and you'll be able to knock them up for your team to collapse, but you ain't gonna drop her.
Blue Kayn however, will. For those that say that it sucks, maybe it's because they're playing it like red kayn and blindly dive in from the frontlines. Has anyone actually SEEN the numbers that Blue Kayn has? It's actually mindboggling how much damage this guy outputs.
The fact that his passive lasts for 3 seconds and during that instance you deal 44% MORE bonus damage on top of your regular damage that can also reset when you use your ultimate. You also gain slow removal and slow immunity. That's... terrifying if you're a squishy.
The arguement: But Blue Kayn gets screwed by tons of CC.
So does Red. Seriously, Kayn doesn't like hard CC chains. Doesn't matter if you're bruiser red with black cleaver and tank items or blue kayn with enough damage to choke a Draven. If they focus their CC on you, you're gonna die.
Another argument: I drop on the ADC and they don't die.
Blue Kayn literally has every tool needed for him to get that kill as quickly on the ADC as possible. A huge range on his slow, a slow immunity, 70% movement speed buff, extra range on his ultimate, a MASSIVE damage steroid with his passive and a means to reset that passive.
If you're unable to get kills as Blue Kayn, then it's something you did wrong, not the form.
and/or 
when the enemy team only had a certain damage type, our team had no tanks, or I wanted the anti-kite benefits of blue as a bruiser. I was able to take some hits but still deal a lot of damage with his passive. Is that ever a good idea on SR, or not really?
top 
jg 
support) because you can burst any squishy and the flanking potential is huge
Boom blue kayne is now red kayne except without the knock up base damages and blue kayne are better than the Q damages anyway blue kayne ahs extra damage passive and blue kayne doesnt have to sit still for w so he kills people even if they dodge his w because they cant attack him if they take the time to dodge his w unlike red kayne. if anything the extended e time dont should have gone to red kayn blue kayne shouldnt have gotten extra time in e (because sitting in a wall longer is assassin like) while getting extra movement speed from it, it should have been either or not both and i expressed that when kayne came out i never even saw a reason to use red form because blue does more damage tanks arent popular and even when they are they either have lots of hp and no armor which makes you good enough with assassin kayne consitent damage or high Armor which is bad because armor blocks less per 100.
or 
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