Cabrón is a versatile and strong Spanish slang word. While it can literally mean 'goat' or be used as an insult like 'a-hole', in this context, it functions as an intensifier.
When the singer says, "El olvidarte se va a estar cabrón," he means that forgetting the person is going to be "damn hard" or "really difficult." It adds a raw, emotional punch to his struggle to move on.
"Vete Y No Vuelvas" is Adriel Favela's blunt farewell to a partner who has broken his trust one too many times. He opens with a simple "Adiós" and tells her flatly to leave and never come back, admitting the relationship has hurt him so badly his heart could barely take it anymore.
Across the song he refuses to fall for her lies again, saying he already feels disillusioned and that letting go of her will be painful but necessary. The chorus makes the finality clear: the damage is done, there is no turning back, and he hopes she eventually learns that love has to be cared for instead of met with fighting and arguing.
He places the blame squarely on her, saying it was her own fault for assuming she would find someone better than him — and now she is the one left regretting it.