Gnar can be antifun
Mini Gnar's specialty is kiting people around so that he can kill them and they can't do anything in return. This is obviously really antifun for the person being kited, but is pretty satisfying for the Gnar player. Frozen Mallet and other items just make this worse, especially against champions without escapes, such as Maokai. Unless they can get on Gnar in their range and fight him, most champions (especially in top lane where basically everyone is melee) can do nothing to Gnar. Gnar also becomes basically unstoppable late game. He is too tanky and has too much CDR and kiting to be easily engaged on and can kite pretty much anyone melee to death. He can often duel ADCs, with only a few exceptions such as Vayne (who should never be used as an example for anything because of how cancerous she is). The only way for Gnar to lose is if he gets destroyed early game, or if he's against someone who is impossible to fight (i.e. Vayne, Jax, etc).
How would I change these things? First of all, I would remove Frozen Mallet from the game. It is only consistently built by Gnar, because he abuses it so well. Then, I would lower the movement speed buff from Gnar's Hyper passive. In compensation, his damage could be buffed in Mini Gnar, since the changes would only affect Mini Gnar. Gnar would still be able to kite, but it wouldn't be anywhere nearly as obnoxious as he is now. One potential buff would be increasing the early game damage on Hyper, since it feels so weak in its first few ranks.
Overall, Gnar is a pretty well designed champion, based on the idea of temporary form changes that can't be directly controlled by the player. He has several built-in measures to keep him balanced, such as the fact that attack speed is only good on Mini Gnar, but makes him turn into Mega Gnar more frequently. He is really fun to play, offering many different playstyles and a really cool kit with a high skill cap. I may be biased, because I am a Gnar main, but I only want to improve the champion. Let me know what you think in the comments below.
Edit: Everyone seems to be thinking that I hate Gnar or something. Gnar is my favorite champion in the game, and he is my main. I love playing him, but a lot of people hate playing against him. If you have ever played someone like a Maokai against a Gnar with Frozen Mallet, you would know exactly what I am talking about. However, Gnar is by no means the biggest problem in the game. He offers a lot of counterplay to much, much worse champions such as Illaoi, Darius, Illaoi, Garen, and of course, Illaoi. However, Gypsylord (the designer of Gnar along with Meddler) has stated himself that he is disappointed that Mini Gnar's weakness, his squishiness, is nullified by the kinds of builds that Gnar usually goes for. If there's anything that I said that is purely opinion and has no basis in fact, please call me out on it. But getting offended and simpy downvoting without an explanation does not make me wrong, or if I am wrong, help me see why I am wrong. Thank you to those of you who commented.

