accidental, unintentional, unintended
Has sido capaz de repetir tu éxito accidental.
You have been able to repeat your accidental success.
— Ratatouille (2007)
Habría encontrado agua de no ser por su muerte accidental.
He would have found water if not for his accidental death.
— Manon des sources (1986)
Fue enteramente accidental que yo llegara a conocerla.
It was entirely accidental that I came to know her.