Overpower is an ultimate Attack ability, requiring level 2 Attack to use. It deals between 200% and 400% weapon damage.
Overpower bears resemblance to another Attack ultimate, Meteor Strike. Overpower deals 200-400% damage, has a 30-second cooldown, and is usable with any melee weapon; Meteor Strike deals 250-350% damage, has a 60-second cooldown, and requires a two-handed weapon. Additionally, Meteor Strike hits all adjacent targets, and it will generate 10% adrenaline for every critical hit until 30 seconds after use. Both abilities average the same damage.
For overall effect, Meteor Strike is preferable to Overpower, but Overpower has a higher maximum hit and no limitations.
Magic has an equivalent of Overpower, titled Omnipower. Both abilities are functionally alike.
Overpower hits 3 ticks after it was cast.