Aalavandaan (2001)

Nandu (Kamal Hassan) is a psychopathic, animalistic man, whose past has wronged him and embedded its mark deep into his soul, creating a personal hell inside Nandu; A hell in which Nandu is living; A hell that haunts him every passing second and with every breath he takes. While Nandu spent most of his life in a mental asylum, his other twin Vijay (Kamal Hassan) was separated from him from childhood. Vijay is the daring commando who is due to marry his girlfriend, Tejaswini (Raveena Tandon), a news presenter for STAR TV, who is pregnant with his child.

Wanting Nandu to share in with their celebrations, Vijay and Tejaswini decide to pay Nandu a visit at the asylum. However the happy events take a dark turn when the dangerous Nandu sees the reflection of his evil step mother in Tejaswini, a person who he truly hated and blames for his life to be ruined. Nandu's mission begins with Tejaswini, who he sees as an evil witch who is going to destroy Vijay's life, just like his step mother spoiled his fathers life. Nandu eventually manages to cunningly escape from the mental asylum and is now walking around free searching for the "witch" that his brother has just wed.

Nandu later comes across popular singer Sharmilee (Manisha Koirala), and both of them fall for each other. When she drugs him, he accidentally goes savage and begins to see Sharmilee as his stepmother, soon he brutally murders her. Later, he becomes heartbroken over his doing and realises that Sharmilee was not his stepmother's re-incarnation.

Nandu leaves the room, but leaves behind strong evidence, through which Vijay deduces him as the murderer. Both Vijay and Teju are advised to leave their city to keep safe from Nandu, and they go to Vijay's ancestral home in Ooty. Nandu however overhears this, and secretly follows them. Vijay and Teju finds Nandu's diary in the old house, which explains all of Vijay and Nandu's miserable childhood days with their stepmother, which led to the death of their biological parents, and also causing Nandu to become an emotionally disturbed criminal who killed his stepmother and resulting in him going to the asylum.

They later find out about Nandu's existence in Ooty through the local police and start to flee, but Nandu follows them. When Nandu finally corners Teju, she begins whacking him with a belt, mirroring the stepmother's usual way of punishing Nandu, convincing him that Teju is indeed his stepmother's re-incarnation.

After a series of events in which Vijay manages to defeat Nandu, the latter sees his stepmother's spirit in a long set of gas tanks and in order to kill her, he lights up a match that causes the tanks to explode, killing him in the process.