Hipnosi' is a colloquial, shortened form of "hipnosis," which means "hypnosis." It's an interesting word because it's not commonly found in everyday song lyrics, making it stand out.
In the song, DrefQuila uses it to describe the powerful, almost trance-like effect his lover has on him. He sings, "Porque tú me hiciste hipnosi' / Ahora necesito de tu dosi'" (Because you put me in a trance / Now I need your dose), conveying an intense, almost addictive fascination and desire for this person.
"Último Día" (Last Day) asks one question and runs with it: "¿Qué haríamos si fuera / El último día?" (What would we do if it were the last day?). DrefQuila's answer is not a bucket list. He wants one more kiss, "que por última vez me beses" (that you kiss me one last time), and he admits he has "esas putas ganas / De que tú vuelvas" (this damn craving for you to come back). It is a breakup song dressed as a hookup song.
He remembers small, specific moments: laughing at nothing "en la madrugada" (in the small hours) and her shouting into the pillow when people were outside. Then it gets steamy and funny at the same time. Chilean slang helps here: "sólo manda ubi'" means "just send me your location" (ubi is short for ubicación), and he says he would get to her even on another planet, "Volando Astro Boy" (flying like Astro Boy, the Japanese cartoon robot). Notice the dropped final s in "hipnosi'" and "dosi'" (hypnosis, dose), a classic Chilean way of talking. The song closes on an English spoken quote: "If you live each day as if it was your last, some day you most certainly will be right", which turns the whole party into something a little darker.