Regarding Ekko's passive
So Ekko's passive deals damage and slows the enemy target on the 3rd auto attack/ability, if the target is a champion, then he gains that amount as movement speed as well. I'm not here to discuss whether this is underpowered or overpowered.
But um why? First of all what's the point of even having a slow on none champion targets? To slow jg camps or minions? It's barely any different from Gnar's W passive. Both deals damage and gives movement speed buff on the 3rd auto/ability. Each champion's passive usually provides the core background of the overall champion characteristic, so why would you put such a generic passive on such a unique champion.