Crimson Gem Loki vs JLA Magnificent 5

Loki with Crimson Gem
VS
JLA:
Superman ( Without Kryptonite/Red Sun weakness.)
Wonder Woman ( Star Sapphire)
Green Lantern ( Hal Jordan). No need to recharge ring)
The Flash
Martian Manhunter ( no fire weakness)

They are fighting in an uninhabited New York.

Do you mean the gem of Cyttorak?

Loki gets phucked up, and bfr'd

Poor, poor Loki

Loki with High Herald physical attributes + his own magic abilities/cunning mind will be tough enemy.