Genesis is a boss in Crisis Core -Final Fantasy VII-. He is fought in the abandoned Mako Excavation facility near Modeoheim. He can also be fought in Mission 5-1-5, although the awards for beating him are different.
The player should start the fight with casting Regen and Barrier on Zack. Genesis's special attack is Black Flurry that it will inflict moderate damage and Curse status. It can be cured with Remedy if Zack is not equipped with any accessories that will guard him from the status effect. Nevertheless, with high ATK and VIT stats, this foe can be defeated quite easily.