Not very merciless (the English title is "Merciless Man"), but a fun detective-"poliziotteschi" nevertheless. Most of the genre staples are present, from chases showcasing the local scenery (not very exciting) to shootouts to villains in high places, but Genova a mano armata sports a rather unique happy-go-lucky charm due to the carefree nature of it's protagonist, played by Tony Lo Bianco.
Maybe it's because I haven't seen a poliziotteschi in a while, but I got a good kick out of this, despite some obvious weaknesses. Lo Bianco appears to be doing most of his own stuntwork, and a few of the fisticuffs are quite well choreographed & performed. The catchy theme song by Franco Micalizzi is very familiar, although the film is one of the rarer ones within the genre, at least as a proper presentation. Genova makes a nice chance of backdrop to Milan & Rome. Humor is present, sometimes also unintentionally.
Most of the reviewers complaining about an incoherent plot must've seen a badly edited version, because the print screened at a showing I attended (35mm, in Italian with custom digital Finnish subtitles) made the story easy to follow despite not making total sense in every twist. Reportedly it was fully uncut & 10 minutes longer than the version currently available on YouTube (without subtitles).