Many actors became stars first establishing themselves as antagonists before turning protagonists. Even now actors who entertained movie lovers as protagonists are now surprising all as antagonists. However, only a few heroes suit negative roles. Cine goers may not accept all heroes in negative roles.
In the olden days, almost all stars did antagonist and protagonist roles. In Parivartana which released in 1954, ANR played the role of the hero while NTR played the role of the villain. However, ANR did not do a negative role. He used to say 'My personality does not suit the antagonist and evil roles'.
Krishnam Raju, Jaggaiah, Kantarao, Mohan Babu, CH Narayana Rao, LV Prasad did negative roles. Even actors like Kannamba, G.Varalakshmi, S.Varalakshmi, Savitri, Shavukaru Janaki, Anjali Devi, Bhanumati, Jamuna did both the roles. However, it is difficult to shine in both roles. The actors' faces and personalities should suit.
Savitri used to say one cannot imagine Suryakantam as heroine and Sriranjani as a villain.