Gnar Bug
In 
's non-Mega form, 
is rendered useless because no matter the amount of stacks you amount, you deal no extra damage
1 Comments
This is intended. The "Crushing Blow" passive of Deadman's Plate will only work for Melee champions. Only melee champions will receive the bonus damage based on the stacks as well as the possible slow. Since Mini Gnar is a ranged champion, he will not benefit from this.
Also, something important to note is that attacking with ranged champions will still use up the Momentum stacks, to prevent them from essentially having a permanent +60 movement speed.