B for Black and Paa
Amitabh is known not only for his blockbuster movies but for giving superlative performances.
In Black, he played a tough-as-nails teacher who teaches a blind-deaf-mute Rani Mukerji, and later suffers from Alzheimer's disease.
He surpassed that by playing a 12-year-old suffering from progeria in the critically-acclaimed Paa.
He also played a Shakespearean actor in the English movie, The Last Lear.