Wake in Fright
aka Outback
(1971)

On an overnight stay before his flight to Sydney for the Christmas holidays, teacher John Grant (Gary Bond) winds up losing all his money gambling. Waking up hung over and missing his flight, Grant is taken in by locals whose idea of hospitality is binge drinking and kangaroo hunting. Grant experiences the dark side of himself, capped off by unwillingly being caught up in a homosexual encounter with Doc Tydon (Donald Pleasance) who takes advantage of him while they are both intoxicated.

Realizing it the next morning and disgusted, Grant waits at Doc's house to kill him. When Doc shows up, Grant tries to take his own life instead. He fails though and his suicide attempt is ruled an accident. Grant gets back on a train and heads back to the town where he teaches, having never gotten to Sydney and seeing his girlfriend. The local bar owner asks how his vacation went. Grant replies, "It was the best" before going back to his room, forever a changed man.

Thanks Spectre!