My biggest fear with Kayn is that he will end up being too weak in the long run
You clearly have defined strong points and weak points and that is cool, but choosing one path over the other may leave him wanting. I already noticed his demon form has no power in the ult leaving it majorly flawed. It say 20% of max hp, but from what I saw, he wasn't doing anything close to that. And he has spell vamp, not lifesteal, which seems to be weak on a melee carry who builds tanky. Idk I may be jumping the gun, but not making it more rounded on either side seems like it has to much draw back. like if you are ahead in the game, are you going to be roflstomped by people who are levels and kills below you because you chose one side over the other? What do you think?