Encabrona is a strong, informal verb derived from "cabrón," which can mean 'goat' but is often used as a vulgar term for 'asshole' or 'bastard.'
In this song, it means 'to piss off' or 'to infuriate.' The lyric "Pero la encabrona que también te quiero" (But it pisses her off that I also love you) vividly expresses the intense anger of his partner upon discovering his infidelity. It's a raw and impactful word that captures the emotional conflict in the song.
This is a confession delivered to the wrong person. "Mi mujer me encontró en el celular los mensajes del WhatsApp" (My girl found the WhatsApp messages on my phone) is the whole plot, and the man telling it is not talking to the woman who caught him. He is talking to the other one. The evidence piles up fast, "Me cachó en las fotos, también los videos" (She caught me in the photos, also the videos), "Ni cómo negarlo, dejé abierto el Facebook" (No way to deny it, I left Facebook open), and his position on all of it is one flat line: "Vergüenza no tengo, pero no me alegro" (I am not ashamed, but I am not happy about it).
What he wants is for nothing to change. "Ella tiene que capear que a las dos les pertenezco" (She has to deal with the fact that I belong to both of you), "Que las dos tienen sus puestos" (That you both have your places), said as though it were an administrative matter. He dresses the affair up as a crossing of worlds, "Tú tan fresa y yo tan cholo" (You are so preppy and I am so cholo), and floats away from the consequences on "En un viaje sideral" (On a cosmic trip). The last line is worth hearing twice: "Que te vi y que me gustaste para el hijo de mi apá" (That I saw you and I wanted you for my dad's son), a boastful Mexican way of saying "for me". Even at the end he cannot quite say it in the first person. LEGADO 7 open the track by dedicating it to Cartel de Santa, and the borrowed swagger never lets up.