Kalyanaraman
Buck toothed Kamal (Kalyanam) is naïve, and the heir to a whole lot of wealth. The manager of the house plot to kill Kamal's father. His dad reveals to Kamal about his twin brother Raman (Kamal, dual role) living in city with mother. The villains kill naive Kamal too by pushing him from the cliff. Innocent Kamal turns a ghost, travels to city and returns with his twin brother to avenge.
Starring Kamal Haasan, Sridevi, Major Sundarrajan, Manorama
Watch "Kalyanaraman" on Amazon released in 1979. It's a action & adventure and drama movie, and has a rating of 6.5 out of 10 from Imdb which is usually fine for this kind of movie, and is currently only available for purchase or rent.