Ekko's Shield
So in one of my games playing against Ekko, I was in some duel against him. He was about half hp, and then gained a shield that filled the entire second half of his HP bar. I knew it had a high AP ratio but… 150%? Really? I get that Tank Ekko using just his bases is crazy, but honestly this is also demented. It also has a giant aoe stun-slow, and an execute on-hit. I legitimately think that with some minor tweaks this could be an Ultimate and nobody would bat an eye.
I think my biggest issues are that while it's delayed 3 seconds, that just makes it so Ekko has to be in the general vicinity. The enemy only gets 0.5 seconds to react, unless Ekko gives a tell. Even if they don't get stunned, it's a hilariously massive shield anyway.
Here are my two suggestions for Ekko's Shield that aren't just 'number' nerfs, but fundamental counter play tweaks. Take either or both.
One: Make the field visible to the enemy for longer. An extra 0.25 seconds will do, even. Two: Make Ekko not get the full shield without stunning a champion.