Pratinayaka is the antagonist or villain in a drama or other forms of Sanskrit literature. In Sanskrit tradition, a pratinayaka is required to be as valorous or great as nayaka, the hero. This can be seen in all forms of Sanskrit literature including poems, novels, play, dramas and short stories. However, unlike a nayaka, who in the dramatic tradition is classified into different types, with respective qualities, not much has been written about the qualities of pratinayaka.
Even in the legends, epics and Puranas pertaining to divine characters, this norm prevails. Tarakasura, the asura who fought with Karthikeya; Ravana, who fought with Rama, Hiranyakashipu, who opposed his own son Prahlada because of latter’s devotion to Bhagavan Vishnu, and so on, were not summarily evil. They had great virtues that earned them boons from gods, including immortality, and which in turn accounted for their arrogance and eventual downfall at the hands of the same gods.
Pratinayaka, thus, is a very complicated construct and not a summary description of a mere villain.
In later dramas in the Sanskrit tradition, there were pratinayakas of smaller stature, too, as in the case of Sakara in Mrccakatikam. In Mudrarakshasa, the pratinayaka of the same name is a less enlightened person than Kautilya, the nayak.