Sucker Punch is an upbeat piano rock piece featuring backing from guitar and drums. The vocals are somewhat low-pitched, and the hook predominantly consists of the piano with backing from the guitar and drums, with synth interspersed throughout. After the song finishes, it loops partially through the vocal section, alternating between this and looping at the start for each subsequent loop. Sucker Punch was one of four songs added in the Splatoonversion 2.0.0. Like all battle songs, it has a random chance of being played during online matches.
In Splatoon 2, Sucker Punch can be unlocked to listen in Squid Beatz 2 as a final reward from the Inkling Squid 2 amiibo. It cannot, however, be heard anywhere else in the base game. It has a maximum score of 206 and 338 in Normal and Hard modes, respectively.
In Splatoon 3, Sucker Punch can sometimes play in the lobby.
Trivia
Strangely, this song, alongside Hooked, features a prominent synth, despite in-universe band Hightide Era featuring no synth player.
In Regular Battles, this song is not fully looped to fit better into two minutes. It shares this trait with Wave Prism and Entropical.
The melody that plays before the lyrics unexpectedly loop repeats exactly eight times. This is very likely a reference to the "suckers" or suction cups of each of an octopus's legs. It only repeats four times in the beginning before the full "sucker punch" is used later.
Etymology
A sucker punch is a term used to describe an unexpected punch. In addition, "sucker" can refer to the suction cups of a squid or octopus, or possibly the "sucker" on the back of a remora.