Thought on Kayn, The Shadow Reaper, after PBE Footage.
First, not OP, so far but he seems to have a nice fair skill cap so we'll wait to see, build hasn't been figured out yet either but Death's Dance is busted right now so it's a must buy on him, especially in Darkin Form.
Form Changes. Base: Very Weak, doesn't deal much damage early, at all really, clears well with Q though in the jungle. Darkin: his Q and R deal more than Assassin form and that's worrying. Assassin: Seems to do very little damage, the ult does almost nothing compared to the Darkin Form.
Reasons: I don't think he'll be TOO broken, definitely strong, but his Darkin Form is overtuned, some changes should be made to ensure that both forms perform their job correctly and as intended, the assassin form seems as though its underperforming.
Future QOL: As an assassin burst is important, Assassin Kayn doesn't have that because his Ultimate deals literally nothing, his passive magic damage is kind of pointless because in the time it would take you to deal enough with it, you'll probably die, which is why i think it should be your First Basic attack against an enemy champion after being out of combat deals Magic Damage on-hit but it would deal more than it currently does.
His R is extremely weak, even though it resets his Passive Damage in assassin form, it doesn't deal any damage, 150+110% of Bonus AD isn't as much as 20+% Max health damage. The problem is that the passive magic damage he get's isn't enough, a good change to his Ultimate could be to make it it apply all of the magic damage instantly, nice bit of burst damage there, instead of just resetting it or to simply have it do what i previously suggested. Both idea's would give him the burst he needs to assassinate a target.
Overall though, the champion seems relatively balanced, so far i'v only seen Redmercy and Brofresco play him, both of them are assassin/fighter mains and they both did well with him but it was VERY obvious that the assassin form is weaker and he does very little damage with his ultimate.
Edit: Also the heal on his E isn't as strong as we thought, it's nice and he probably needs it, kind of wish his E couldn't be used in combat though cause that will get annoying buuuuut i digress.