Pedazo de tonto literally translates to "piece of a fool." It's an idiomatic expression used to call someone a complete fool or an idiot, often with a dismissive or exasperated tone.
In this song, the singer declares, "Se le acabó su pedazo de tonto" (His 'piece of a fool' is over). He's asserting that he's no longer going to be taken advantage of or treated like a fool by his ex-partner, signaling a shift in power and his newfound resolve. It's a memorable and impactful phrase that captures the song's theme of moving on from a toxic relationship.
"Pedazo De Tonto" is Carin León and Luis Mexia's answer to being taken for granted. The singer catches his partner spreading rumors about him online, and instead of chasing her down to explain himself, he walks away.
The hook is the turning point: his days of being her fool are over. He's done begging, and now he wants the roles reversed. He tells her to let go of whatever doesn't serve her anymore, and that she'll only realize what she lost once it's too late.
It's a confident kiss-off more than a sad breakup song. He's not bitter, just certain that walking away was the right call, and that time will prove he was the best thing that ever happened to her.