Ravana’s sin

Like his brothers Kumbhakarna and Vibhishana, Ravana is fully aware in his inner being that he has committed a sin in taking Sita forcibly from Rama. But his vain-glorious conceit does not allow him to accept his error or retrace his steps, said Sri Jamadagni in a lecture. That is why he is unable to extricate himself from the danger and rejects the valuable advice of Vibhishana.

Right from the beginning, Ravana’s close advisers boost his confidence and recall all his previous successes that stand testimony to his extraordinary valour and strength. They talk only of his successes in subduing the celestial beings, the dhanavas, and the gandharvas, etc and his invincible powers, and do not dare to mention the grave sin in abducting Sita slyly and forcibly. Only Vibhishana is outspoken in this regard for, his inherent dharma cannot espouse adharma. He strongly advises Ravana to restore Sita to Rama and save Lanka and the people from destruction. Ravana is angered by this advice and Vibhishana parts from the sinner and seeks surrender at Rama’s feet.

Kumbhakarna is also a noble soul and tells Ravana

that he had ignored the principles of statecraft and had
not consulted the council before committing the sin.
But his loyalty and love to his brother outweigh his sense of dharma and so he continues to support the erring Ravana wholeheartedly.

When Ravana seeks his advice on the eve of the battle

after the rakshasa army had faced considerable losses,
Kumbhakarna only reiterates Vibhishana’s solution to
the inevitable peril in incurring Rama’s enmity.
Kumbhakarna is under no delusion about Rama’s
supremacy and the limitations of the Ravana’s boons
and points out that Ravana will have to face the
consequences of his serious offence soon in naraka loka.