Guide on how to nerf ekko:
Make his passive slow you by 15-50% decaying over 2-3 seconds 1-18 Gives him 60% Movespeed decaying over 1.5 - 2 seconds if he gets 3 stacks. --Damage removed Ekkos movement speed is capped at 450-475 including ONLY boots and abilities. If he hits this limit, he goes into Z Overdrive Z Overdrive: Ekko has 550 movement speed that is in-reducable for 1.5+.5 per 125 AP second(s) but all of his abilities are disabled except for his ultimate. His ultimates clone only becomes 2 seconds behind. Each autoattack grants Ekko 2-5 armor and magic resist, he gains 20-50% attackspeed, and each autoattack does .1-.25 of his ap
His Q should do more damage on the way out instead of on the way in. I get that you're supposed to be tricky with it to maximize damage but I honestly never understood why a champion intended to be a burst assassin had an ability that did more damage after a delay.
How about like 50 damage + .5 AP on the way out and 30 damage on the way in + .2 AP
I won't touch on any other part of his kit except maybe lowering his ult ratio to 1 instead of 1.3 because I really love how his kit rounds up together. These are just some suggestions.