Time to see 
threads until either: A) the item is fixed or B) Gnar gets nerfed
Just make the item melee only. It has stats that really only melee champs want, and it has incredibly toxic interactions with ranged champs that arent balanced to have a permaslow in their kit, so when they win trades it means that the other champ just dies
doodlebob6661 voteseven on melee's its toxic, since it takes away the skill checks built into their kits to allow them to stick, the item itself is toxic and needs to be removed
DeusVult1 votesfar less so than it is on ranged champs, but Gnar takes the cake, since he gets the awesome 1v1 potential from the items passive, but also "double dips" because of how good the huge health investment is on him when he goes into Mega Gnar form
Slythion1 voteswhen Gnar isn't even strong but players call for "nerfs" instead of "rebalancing" because of a toxic interaction, because somehow that has to do with balance an not enjoyment???
sad lyfe :'(
DeusVult1 votesGnar, if frozen mallet was removed or made melee only would be fine
Gnar with frozen mallet is a sideline monster that only a handful of champs can deal with.
but then again same goes for most of the other splitpushing ranged champs
with mallet is almost impossible to kill
same for this asshole
with is the second most picked ADC in LCK atm
Slythion1 votesfalse, and I really hate this type of thinking despite it being incredibly common on the boards. I'm not mad at you, but let me explain:
A champion's strength is determined by statistics, numbers. As of right now Gnar sits at 49.84% winrate with a 5% play rate. Those numbers are not even remotely OP. They aren't unviable, but they show that Gnar is now out of place from an actual balance perspective.
What you and so many others among the boards do is confuse toxic or unfun gameplay with being op. Syndra is another great example of this as she sits at a 47.98% win rate w/ 6.74% play rate.
Gnar with Frozen Mallet is not fun. It's toxic and creates an unfair atmosphere. But even with that toxic gameplay he sits with those sub-par to moderately-strong statistics, despite Frozen Mallet being incorporated in both his most common and his most successful builds.
If you think Frozen Mallet is such a problem and wish to remove it without any compensation, you should recognize that you, from your very own reasoning that Mallet is op, would be gutting a champion that barely gets by even with abusing the item.
So this leads us to a very simple question to ask, but usually a pretty difficult question to answer:
How would you compensate Gnar, if you were granted the nerf or removal of Frozen Mallet?