Anhelo translates to "longing" or "yearning." It's a beautiful and evocative word that expresses a deep, heartfelt desire for something.
In "Mi Mayor Anhelo," the singer uses it to convey his profound wish to be everything to his beloved, singing, "Es mi mayor anhelo" (It's my greatest longing). This word perfectly captures the intense romantic desire at the heart of the song.
Banda MS spend three and a half minutes on a single idea and never tire of it. The song opens by pointing at the singer from the outside, "Mira cómo este loco" [look how this crazy guy], as though he needs somebody else to explain the state he is in. Only after that does he take the sentence over and speak for himself.
What he asks for turns out to be oddly domestic. He is not after grand gestures. He wants "El calor de tu cama" [the heat of your bed], and the ordinary business of belonging to one person for good. The title line, "Es mi mayor anhelo" [is my greatest longing], lands only after that list of small things, which is exactly why it lands. The second half then repeats the chorus without altering a word while the brass pushes harder underneath it, so the repetition comes across as insistence rather than padding.