What would you say is the most accurate portrayal of a real life event in a movie?

Could be any movie so long as it’s based on a true event or person’s life. I know none are going to be 100%, but I wondered which are at least the MOST accurate. For example, I heard A Beautiful Mind was really all bullcrap. There are a lot of others I wondered, like Papillon, The King’s Speech, Argo, Serpico, The Great Escape and others I’m too tired at the moment to think about off the top of my head.