Normal: "Once the most powerful of all fiends. With the coming of more formidable Weapons it has relinquished that title, but it remains a mighty adversary nonetheless." Oversoul: "Even more powerful in its oversouled form. It appears to be highly cognitive. For example, when attacked with magic, it considers how to respond."
The Omega Weapon is an enemy from Final Fantasy X-2. He can be fought repeatedly as a normal encounter at the Farplane; a downgrade from the superboss of Final Fantasy X. However, he is still a powerful adversary, as he can inflict Itchy with its normal attack, and hit the entire party with its powerful Judgment attack. It is highly advisable to set up Protect at the start of the fight and hit it with the best attacks that each party member is capable of using. Excalibur, Black Sky, Supernova, and the like are all ideal for tackling Omega Weapon. In Oversoul, it has access to Flare, which should be countered by using Reflect. It becomes much easier to defeat when in Oversoul form.