Bandolera literally translates to "bandit" or "rogue," often referring to a female outlaw or a person who acts unscrupulously.
In this song, Marc Anthony uses it to describe a woman who has deeply hurt him, implying she is deceitful and has played with his emotions. It's a strong, evocative word that conveys betrayal and heartbreak, making it memorable and impactful.
Juan Gabriel wrote this as a slow ranchera about being ruined by love. Marc Anthony turns it into salsa, which is a strange and brilliant decision: the horns are having a party while the man at the microphone falls apart. He opens by describing who he used to be. "No sabía de tristezas" (I didn't know about sadness), "Ni de lagrimas, ni nada / Que me hicieran llorar" (no tears, nothing that would make me cry). Nobody says that about a life they are still living.
Then the title arrives. "Hasta que te conocí" (until I met you), "Vi la vida con dolor" (I saw life with pain). The line that makes this better than an ordinary breakup song is the one right after, where he refuses to tidy up the story: "No te miento fui feliz" (I'm not lying, I was happy), "Aunque con muy poco amor" (although with very little love). He admits he got something out of it. By the last verse he has given up on being fair and is throwing "Sí muy mala conmigo" (yes, very cruel to me) over the band, and the song runs out in ad-libs with the trombones still going.