Maldades is the plural of maldad (wickedness), and it translates to "wicked deeds" or more playfully, "mischiefs". It's a fantastic word that perfectly captures the song's core theme of being a 'Mala Santa' (Bad Saint).
In the lyrics, Becky G sings "Apaguen celulares, estamos para maldades" (Turn off your cell phones, we're here for some mischief). She's using the word to describe a night of rebellious, playful fun, rather than anything truly evil, making it a memorable and expressive word to learn.
Becky G is here to tell you that people aren't simple, and she's definitely not. The whole song is a warning not to put her in a box. She states it clearly in the chorus: "No soy ni mala ni santa" [I'm neither bad nor a saint]. She knows people think she's trouble—"Dicen que hay peligro cuando salgo" [They say there's danger when I go out]—but her point is that she contains both sides. She can be the quiet girl, "calladita," but also the wild one who, once she gets going, doesn't want to stop.
This song is all about her owning her desires and having a good time on her own terms. She's not looking for a relationship, flatly stating "No me hablen de amor / Eso a mí no me interesa" [Don't talk to me about love / That doesn't interest me]. Instead, she wants to party "hasta el otro día" [until the next day] with tequila and dancing. She's in complete control of her own fun and sensuality, telling her dance partner that the game has started because she decided it would.