Oh the AgonyG 20

Oh The Agony!
"As Hades, land a single Pillar of Agony on 3 enemy gods affected with Blight."

Blight:
Hades's Passive Ability. It adds a debuff to an enemy and adds an additional effect to Hades's other abilities. To apply it to an enemy, just hit them with an auto/basic attack (It lasts 5 seconds.)


Normal Way: Play a game of Arena. Buy attack speed items. Reach level 5 to earn your Ult. Find 3 enemies clumped up (and hope that they don't flee or insta-kill you.) Just basic attack them 3 and use your Ult with cn_Y It should unlock almost instantly.

However, it may be glitchy in a good way!:
In my experience with this achievement (twice on two separate accounts) and seeing other comments on it among different places, it seems to unlock with different requirements. On my first account, I got it by inflicting Blight on 2 or 3 minions and 1 Skadi. On the second account, that didn't work. I had to unlock it legit. So I'm not able to write a full proof glitch guide because I'm not sure exactly what's unlocking it so hope you get lucky.