Gnar is overwhelming in late game teamfights, something should be adjusted

TL;DR "Gnar is outstanding in team fights, and his versatility makes him viable in almost all circumstances within those teamfights."

Time and time again I roll into a ranked game against/with a Gnar, and the same thing happens. Gnar does below average in the laning phase, and starts roaming a bit early. Nothing too unusual for some solo top champions, but after the 25 minute mark you can forget about an easy victory, even if you slaughtered the rest of Gnars team, and kept him from getting too much farm/kills. Gnar hits a point in the game around the 25 minute mark, and it seems regardless of how held back he was early on, its all straight uphill (This uphill would be a cliff for Gnar) from there. His teamfight potential is so massive, even when people know to spread out, and try to avoid him when his ult is about ready. On paper there are a lot of counters to Gnar, but when you factor in the summoner spells, and his gap closing there is not a lot of room for error, and Gnar (Particularly mega Gnar) can turn the tide of a team fight by an incredible margin.

Suggestion: Add an extra 0.2 second cast time to Wallop. OR Reduce the range of Crunch from 475 to 450, and reduce the damage dealt to your maximum health from 6% to 5%.