Cadenón is formed by adding the augmentative suffix '-ón' to the word cadena (chain), transforming it to mean a massive, heavy chain or flashy jewelry.
In the song, C. Tangana sings about sleeping with his cadenón on because he spent so many nights dreaming of feeling its heavy weight. He uses this striking image to represent his ultimate success and wealth, creating a tragic contrast when he realizes these material things mean absolutely nothing without the person he loves.
This song is one of the saddest flexes you'll ever hear. C. Tangana lists all the signs of his success—"Guccis en el closet / Cien mil en una noche" (Guccis in the closet / A hundred thousand in one night)—but it all feels completely empty. He even says he's tired of winning: "Me he cansao del primer puesto / Ya no quiero ser mejor que el resto" (I'm tired of first place / I don't want to be better than the rest anymore). Why? Because the person all this success was for is gone, and he makes it clear that "todas las cosas / Que importan se fueron contigo" (all the things / that matter left with you).
He's so desperate to feel anything other than this pain that he presents three wild options to his ex. He asks them to either give him a distraction, hurt him physically, or just lie to him. The chorus is a plea: "Mejor dame otra calada / O párteme la cara / O miénteme y dime que me quieres" (Better give me another drag / Or smash my face / Or lie to me and tell me you love me). It's a brutal and honest look at how hollow fame and money can feel when you're heartbroken.