In 1942 who won an acdemy award for best actor in diary of Anne Frank?

The film "The Diary of Anne Frank" was released in 1959, not 1942. It is a dramatization, not a documentary, of Anne Frank's life.

While there were several actors nominated for Oscars in 1959, no one won an Academy Award for Best Actor for "The Diary of Anne Frank." The award went to Charlton Heston for his role in "Ben-Hur."