All-Out Attack
From Megami Tensei Wiki: a Demonic Compendium of your True Self
All-Out Attack, also known as 総攻撃 (Romaji: soukougeki) or フルボッコ (Full-bokko among fandom) in Japanese, is a battle tactic in the Persona series. It is first introduced in Persona 3. As it name implies, triggering the command allows all characters to strike all enemies together at the same time.
Unlike Fusion Raids or Fusion Spells, the prerequisite to trigger the action of All-Out Attack requires more than one character in the battlefield, meaning the Protagonists cannot initiate All-Out Attacks by himself alone. Furthermore, all enemies on the battlefield must be knocked down in order to trigger the All-Out Attack command.
However, there are several instances, that even though all enemies are knocked down, the All-Out Attack command will not initiate. This might be caused by the fact that an enemy is defeated while knocked down with the other being alive, albeit knocked down. While late in-game boss enemies are mostly without weaknesses, the All-Out Attack can still be triggered should the boss enemy misses a physical based attack and slips, "knocking down" itself or if the boss is hit by a critical hit.
The damage of an All-Out Attack is based on the normal weapon attack damage of each character and the total present characters in the battlefield. Thus theoretically the more powerful the characters' weapon are, the more damage the All-Out Attack inflicts. All-Out attacks also deals more damage should there's only one targeted foe, rather than a group. It should also be noted that All-Out Attack is Physical Almighty based, meaning it cannot be voided, repelled, or absorbed. However, the damage of an All-Out Attack can still be severely withered should the targeted enemies resists Physical and/or Almighty-based attacks.
Alternatively, such graphical style actually exists in Persona 2 which is a fusion spell, Triple Charge (トリプルチャージ), that requires 3 Personas to perform the "Attack" (戦技) type skill Tackle (体当たり) together. This technique deals large Attack type damage against 1 foe.
