SMITE

As Martichoras, reach maximum stacks of Monstrosity in a single game.

This one may take a little while.
Monstrosity is a part of Martichoras’ passive ability. You can get a maximum of 30 stacks in a game. However, you only get stacks of Monstrosity by first earning stacks of Ferocity.

You can gain up to 100 stacks of Ferocity at a time. Ferocity is earned by hitting basic attacks, abilities and earning kills or assists. Once you reach 100 stacks of Ferocity, all 100 at consumed and you gain a buff. You also pick up 1 stack of Monstrosity.

Ferocity then starts stacking from 0 again.

For this achievement, you need to get 30 stacks of Monstrosity in a single game. So you’d need to get 3000 stacks of Ferocity which automatically convert over time.

I’d recommend trying this in one of the longer game modes where, or one where you’ll be able to safely go off and farm as well as be part of the team attacks, like Conquest, Slash and possibly Joust.

You’ll want to be attacking anything and everything in order to build stacks, with all types of minions and jungle monsters counting towards stacks as well as god kills and assists. I’d recommend building attack speed along with regular hunter items simply so you can get off more attacks throughout the game. The item Odysseus' Bow is recommended here as the items effect chains attacks between enemies nearby, all of which count as stacks.