The Last Laugh

As far as I know he starred in some important Nazi movies at the time.

In the first years of Hitler's rule he was a Nazi enthusiast, but then many Germans were before the horrors of war came to show them a different side of the Fuhrer. After the war, as a result of the de-Nazification carried by the Allied occupiers among those who had supported the regime (Leni Riefenstahl among them) Jannings was black-listed by the post-war German liberal intellectuals, to the point that he would barely get any work at all for the rest of his life. He died virtually penniless and forgotten, in the Fifties, I think.
A sad story for a great actor who was the first ever to win an Academy Award.