SMITE

As Ao Kuang, get a kill with Water Illusion (first ability, the one where you go invisible).

This is easily done on Arena. First, get (or find) an opponent who has minimal health, then triple tap ability 1 when you are near them, this should kill them instantly.

To get this quicker, level up your first ability as frequently as possible, and buy cool down reduction items (Chronos' Pendant and Breastplate of Valor)

This is actually a fairly easy achievement and I've included a video of the achievement legit for demonstrations.

Water illusion is your first ability and does more damage than people realise. Simply lay the trap and wait for a low health enemy to cross it.

The tactic below using Ares works well, as does Odins ultimate.