Maldecío' is a colloquial, shortened form of "maldecido," which means "cursed" or "hexed." It's a strong and dramatic word that stands out in the lyrics.
In the song, Darell uses it to express the intense feeling of emptiness and misfortune he experiences when his love interest isn't with him. He contrasts it with "bendecío'" (blessed), highlighting the profound impact her absence has on his emotional state.
Darell's "Mundo Imaginario" throws us right into the head of someone completely obsessed! He's so lost in thought about this person that "Todo el mundo dice que estoy loco" [Everyone says I'm crazy] because he's always talking about her. He spends his days "Perdido mirando tu foto" [Lost looking at your photo] and living in this "mundo imaginario" [imaginary world] where she's always with him.
He's desperate to see her again, asking "Dime cuándo te vuelvo a ver" [Tell me when I'll see you again] and promising to do "qué hay que hacer que lo voy a hacer" [whatever needs to be done, I'll do it]. Even her attitude doesn't bother him; he wants her "con to' y tu actitud" [with all your attitude]. But as time passes and he's "solito en casa" [all alone at home], his imaginary world starts to feel less like a dream and more like a torment, especially when he's "Buscando la cura pa' aliviar los dolere'" [Looking for the cure to ease the pain]. He misses her so much he's constantly imagining her there, wishing those fantasies were real.