Malandro is a slang term used in many parts of Latin America for a gangster, thug, or troublemaker. It evokes a 'bad boy' image, often associated with street life and illicit activities.
In "POR ESOS OJOS," the singer dramatically declares, "Por esos ojos me hice malandro" (For those eyes, I became a thug). He uses this powerful word to show the lengths he'd go for his love, framing his tough persona as a direct result of his devotion to her.
In "POR ESOS OJOS," Fuerza Regida mixes street-level bragging with absolute obsession over someone's gaze. The narrator admits that wealth changed him, wearing "una cadena con diamantes" ("a diamond chain") after pulling himself out of poverty. But all the fast living, fame, and cash leave an empty spot. He bluntly confesses that "el billete no vale verga" ("money isn't worth shit") when set against how he feels about this woman. You get Mexican slang right away with "me la paso a toda madre" (meaning he is having a great time) alongside threats for haters, claiming "pa'l envidioso cargo aparatos" ("for the envious guy, I carry heat / weapons").
The real hook of the song is the extreme, reckless romantic talk. He claims "por esos ojos, yo robo y mato" ("for those eyes, I rob and kill") and "por esos ojos me hice malandro" ("for those eyes I turned into a crook"). It is completely over the top, but it shows the dangerous lengths he will go to impress someone he calls "la envidia del antro" ("the envy of the nightclub"). Even with all his tough talk and promises to protect her from heaven if he dies first, his main goal stays simple and direct: begging her not to say no tonight.