Question

in 1950 he won
a tony for best play
& 18 years after
his 1965 death,
he would go on to
win 2 tonys for
a musical

Explanation:

The person won a 1950 Tony for Best Play, died in 1965, and 18 years after his death (1983) won two Tonys for a musical adaptation of his work. This matches Tennessee Williams: he won the 1950 Tony for Cat on a Hot Tin Roof (Best Play), died in 1965, and in 1983, the musical adaptation of his A Streetcar Named Desire won two Tony Awards (Best Featured Actress in a Musical and Best Lighting Design in a Musical).

Answer:

Tennessee Williams