Gnar is broken and should be nerfed , that's why .
Gnar can deal much damage, has the potential to have good CC andis tanky - BUT:
He can only play this out if his opponent let's him.
His abilities (transformed) have a noticeable windup.
While small HE HAS NO ULTIMATE.
Both of his stuns are unreliable, especially his ultimate requires his opponents to be OUT OF POSITION.
Gnar is a champion that does well against bad players with low reaction time who tend to misposition.
Thus: SoloQ
Gosh, I love how people these days are too bad for the simplest amount of counterplay.
Gnar has a big indicator beneath it name. Use it against him.
If he transforms and you are a bad player - stay away from him and wait for it to run out.
If he transform and you're a semi decent player - dodge his THAT BIG FREAKIN RED RECTICLE. Or use the 2 days windup on his Q to dodge it.
Transformed Gnar is slow he can be easily kited.
Not to mention that champions like Pantheon or Wu can completely deny or even kill Gnar at levl 2.
Or Zed e.g. will always dominate Gnar with his mobility.
Most people completely fail to realize that they can use Gnar's passive against him. There are times where you truely don't want to change.
Last hint how to destroy Gnar:
Pick Vayne top.
Once Gnar is transformed there's absolutely nothing he can do if you tumble his W. (Just don't stand next to a wall when his R is up).
If Mega Gnar jumps in and misses EW he is completely helpless against Vayne due to his horrible mobility.