Vete is the command form of the verb irse, meaning "to go away" or "to leave." It's a very direct and emotionally charged word, much stronger than a simple adiós (goodbye).
In this song, the singer uses Vete to forcefully tell his ex-lover to leave his life for good. This single, powerful word captures the pain and finality of a difficult breakup, making it the central theme of the entire song.
This song is the ultimate breakup anthem for anyone who's tired of being the second choice. The singer lays it all out from the start: "Nunca pensé que fuera tan difícil / Tenerte a mi lado sabiendo que tienes a alguien más" (I never thought it would be so hard / to have you by my side knowing you have someone else). He's been in a painful love triangle, but he's finally decided to end it.
He doesn't just ask the person to leave; he commands it. He says, "Vete, ya no vuelvas a llamar" (Go, don't call again). It's a firm and final decision. While he admits "Duele, pero te voy a olvidar" (It hurts, but I'm going to forget you), he's choosing his own peace of mind. The song is a powerful statement about respecting yourself enough to walk away from a situation that's causing you pain.