Harry Dunning is a character in 11/22/63.
On October 31, 1958, (1960 in the Hulu miniseries) Harry was preparing to go Trick-Or-Treating. His father, Frank Dunning, came in with a sledge hammer and killed his estranged wife, son and daughter. Harry was injured but survived. The attack left him with brain damage and a dislike of Halloween.
Jake Epping went back in time from the 21st century and prevented the murders by killing Frank while he was assaulting his wife. Back in the present, Jake discovered that while he saved the family, Harry was killing serving in Vietnam.
In the timeline in which Jake stopped JFK's assassination, Harry was a widower living in dystopian Lisbon Falls, Maine. After meeting Jake upon his return from 2011, Harry details the history of the world dating from 1963, including earthquakes, several nuclear exchanges and general lawlessness.
In the television series, after the family was saved, Harry becomes a homeless man. He is portrayed by Leon Rippy.