Bandido literally translates to "bandit" or "outlaw". It's a fantastic word that paints a vivid picture of a wild-west style robber.
In this song, Ana Bárbara uses it as a nickname for a lover who has "stolen her heart". She calls him her "bandido", portraying him as a charming, irresistible heartbreaker she is determined to catch. This metaphorical use turns a word for a criminal into a passionate term for a captivating but troublesome lover.
Ana Bárbara kicks off this Regional Mexican anthem in the pit of post-breakup regret, cursing the sleepless night she spends remembering the wrong person who stole her heart: Mala noche / Recordarte enamorada / La persona equivocada / Alguien que robó mi corazón ("Bad night / Remembering you in love / The wrong person / Someone who stole my heart"). She admits she was a fool trapped by his seduction (Atrapada por tu seducción), dying without his kisses while waiting for him to come back. Most people wallow in the dark, but she takes that sadness and turns it directly into a hunt.
That turns the whole track into a high-energy pursuit. She calls him a criminal and vows retribution: Te buscaré bandido / Te atraparé maldito / Te lo juro / Pagarás por mi amor ("I will search for you, bandit / I will trap you, damned one / I swear to you / You will pay for my love"). Here, calling someone a bandido frames the lover as a thief who got away with her heart, while maldito adds plenty of bite to the threat. She warns that an infatuated woman is capable of anything (La mujer que se enamora / Es capaz de cualquier cosa). It is dramatic, funny, and completely focused on settling unfinished business between their two hearts (tienen algo pendiente los dos).