Warriors All-Stars

The gameplay is modeled after the hack-and-slash Warriors series, in which the player controls a single character to defeat enemies throughout a stage while trying to achieve a specific goal. In Warriors All-Stars, each player may also select four supporting characters to assist the chosen character; the supporting characters lend additional abilities that may be triggered by holding down R1 and selecting a face button. Certain pairs of characters, when assisting the character at the same time, may combine their attacks for additional effect.

Source: Wikipedia, "[en.wikipedia.org/wiki/Warriors_All-Stars Warriors All-Stars]", available under the CC-BY-SA License.