Time to nerf Gnar
I know I will get a lot of hate for this post, but it's true. Gnar is just too strong right now. He has the same problem as Ekko, way too may things in his kit.
Long range attack with a slow. Check. Percent max health damage. Check. Increased movement speed. Check. Mobility with built in single target damage. Check. CD reduction. Check. Another long range attack with AoE damage and slow. Check. 1.25 second AoE stun with damage. Check. More mobility with AoE damage and slow. Check. Another AoE stun with damage. Check.
Let's face it, his kit is loaded to the gills. His weaknesses. Kind of squishy in mini gnar form, but good luck catching him. Being able to predict when he changes form. That's really it. Counterpicks: Quinn (who is rarely if ever played) and Irilia (if she is really good). That's pretty much it. Everything else is a skill matchup at best. He is very hard to kill in either form because he either gets away or is just way too tanky. Plus you can't get away from him due to his mobility and slows in either form. Who can honestly argue that he doesn't need nerfing.
. With what Gnar

and you beat him.