I guess I'll start

https://www.quora.com/What-famous-actors-actresses-have-been-blackballed-in-Hollywood-and-why-Do-any-of-them-get-over-it-to-regain-work/answer/Jon-Mixon-1

The late Cliff Robertson was blackballed in Hollywood due to his reporting a fraud that involved a rogue studio executive embezzling money and using Robertson’s name to do so. Although the executive was fired, Robertson was told not to report the matter as it was a relatively common practice. Robertson did and both he and his wife, actor Dina Merrill found themselves blackballed for roughly five years.

Robertson’s career “righted itself” after that point. However he never regained the popularity that he experienced in the late 1960s and early 1970s and he became a character actor who never again had leading role in a film again. Robertson died in 2011.

loved him as the president in escape from l.a.

"Charly" was one of my favorites.

Cliff Robertson was always one of those weird actors for me whose face I know and name I recognize but constantly kept confusing for other actors or misremembering the roles he starred in. For example, when I first saw his name pop up in MC I thought, "Wasn't he the guy in Untouchables?" But no, it was Robert Stack.

I can't believe he's been gone ten years already. I could swear I just saw him in a new movie not that long ago.