The overall tone of this HBO Max series is mostly action comedy. There are a lot of gags, quirky dialogue and puns made by the characters, while other moments are more brutal for comedic effect. The gore is also a big part of the series and it doesn't shy away from it, but it's not the main focus of the series, it's just used very efficiently to make you laugh.
However, if the whole thing works is because of John Cena, as he brings his A game comedic skills into play to make such an unlikable character so endearing. He brings such a vulnerability to such a though character that it's impossible not to root for him, even though he commits horrible acts of violence along the way.
The rest of the supporting cast is ok, but Cena steals every scene he's in. Despite its faults, Peacemaker is a fun show, even if it doesn't justify its existence in the DCEU. But after watching many super dark and gritty DC TV shows that take themselves too seriously, this is certainly a much appreciated levity in the otherwise dark and gloomy franchise.