As Persephone, trap the entire enemy team with one use of her Grasp of Death ability.
UPDATE Persephone is currently banned in Duel as it is a Ranked game mode and a newly released God/Goddess is always banned in Ranked mode for balance. Once Persephone is put into ranked mode I will still test if it's unlockable in Duel. For now Joust seems to be the best option.
With the description, you
SHOULD be able to obtain this in 1vs1 Duel being the easiest option, or 3vs3 Joust. Since the entire enemy team in Duel would be a single person and 3 people in Joust as opposed to 4/5 in other modes. I will test this on release and update the solution accordingly.
Grasp of Death is Persephone's Ultimate ability and is described below.
Persephone conjures a mass of Entrapping Vines that she throws forwards, entrapping the first enemy god or wall it touches. Entrapped gods are crippled, rooted, and have reduced Attack Speed. Vines then spawn from the Entrapped target that seek nearby enemy gods. Upon finding an enemy god it binds them, crippling them and preventing them from moving away. Entrapping Vines are destroyed if hit by 5 Basic Attacks, ending all effects.
So any part of the trap shall do. If this does not work for either modes you are looking at the new Ares style achievement.
Below is a video showcasing her ability kit. Grasp of Death is showcased at the 3 minute mark. Video provided from the developers of SMITE.
Feel free to shout with any questions, comments, or concerns.
~ Slayer