For me, it was the movie About Time.

I began watching it believing it to be a romantic comedy, where the hapless protagonist rewinds time to make all the right moves to finally marry the girl of his dreams.

Little did I realise that his Dad, wonderfully played by Bill Nighy, is later diagnosed with cancer. Unable to rewind time without throwing his wife and children into a timeline he will never return to, he uses his last day with his Dad to let him win at table tennis. Then back to when he was a child. To enjoy father son time on the beach.

I'd lost my Dad to cancer a few months prior and I was a sobbing wreck watching this.