Refers to a deep-seated feeling of ill will.
A pesar de su rancor, decidió perdonar a aquellos que le habían fallado en el pasado.
Despite his rancor, he decided to forgive those who had let him down in the past.
El rancor que siente por su compañero de trabajo es innegable.
The rancor he feels for his co-worker is undeniable.