However, there is an intriguing backstory involving the two actors. In an old interview with Hindu Tamil Thisai, veteran filmmaker K. Bhagyaraj revealed that Amitabh Bachchan felt insecure about Kamal Haasan’s talent and decided to withdraw from a project midway.
This incident dates back to the 1980s, when Amitabh was at the peak of his career and Kamal was rapidly rising in prominence. They were cast in a film titled ‘Khabardar’, directed by T. Rama Rao. The social drama revolved around a terminally ill patient, played by Kamal, and a doctor, portrayed by Amitabh. Jaya Prada and Sridevi also starred in lead roles.
After major portions of the film were shot, it was unexpectedly shelved. In a later interview, Kamal Haasan mentioned that the project was stopped midway and he received half of his remuneration. Director K. Bhagyaraj later disclosed that the film’s script required Kamal’s character to die, which he believed would overshadow Amitabh’s role. Concerned about his character's impact, Amitabh chose to exit the film, offering bulk dates to the producers as compensation.
Although ‘Khabardar’ was never completed, the two actors successfully collaborated in ‘Geraftaar’ in 1985.
Source : Bollylah, OTTPlay