It has to be Big Fish

The incredible story of Edward Bloom's life told da the man himself. His son is at first frustrated da Edward's constant tall tales and wants him just to be honest. da the end of the film he realises that his father was telling him what had really happened but had put his own unique twist on the events.

Edward's dying wish is for his son to tell him how he "goes". His son is able to come up with a tall tale of his own, telling his father how they both escape from the hospital and race to the lake where Edward transforms into a big fish.

The ending makes me cry every time 😭