Resenti'o is a colloquial pronunciation of resentido, which translates to 'resentful' or 'hurt'.
In the lyrics, Beéle sings, "Mi cora' está resenti'o si tú no me besas" (My heart is hurt if you do not kiss me). He intentionally drops the 'd' in resentido, which is a very common accent quirk in Caribbean Spanish and urban music that is essential for language learners to recognize.
This song is one big, confident message to an ex, or maybe a current partner after a fight. Beéle is basically saying, "Ignórame to' lo que puedas / Pero de ninguna manera / Podrás olvidarte de mí" (Ignore me all you want / But there's no way / You can forget me). He's completely sure that what they have is so intense and memorable that she'll never be able to move on. He reminds her of a specific romantic night they shared under a full moon, convinced that memory is permanent.
He also admits their relationship is a bit wild. He calls it a story of "'Amores' / Dementes" (Crazy loves), acknowledging that they fight over stupid things all the time. But he sees their shared craziness as a perfect match: "Tú eres loca, yo soy loco / ¿Qué más quieres?" (You're crazy, I'm crazy / What more do you want?). Despite the drama, he can't stand to be without her, saying he goes crazy and isn't happy when she's not around. It's a song about a passionate, slightly chaotic love that he believes is absolutely unforgettable.