Oscar-Winning Supporting Actor From a Biopic

Portraying a real person in a biopic is a challenging feat for actors. Capturing the essence of a well-known individual requires immense skill, and their performance is closely scrutinized by both film fans and readers of the biopic's source material. Success in this role can bring great rewards, including the coveted Oscar statuette.

Thinking about actors who won Oscars for Best Actor in a Supporting Role for biopics, who do you think delivered the most iconic performance?

Please discuss here.