Marisa Tomei.
She won a well deserved Oscar for her role in My Cousin Vinnie. But as with many things, a rumor started floating around that Jack Palance either said the wrong name or disliked the actual winner so much that he blurted out a wrong name. Marisa was not thought of as likely to win an Oscar, the competition was fierce, great movies and awesome actresses. No matter how you look into it, she was awesome in her part, so awesome that many (nasty) people thought she was just herself, not acting and simply did not deserve it.
But as for conspiracy theories, things simply don’t work that way. This was a nasty story from a nasty person who you need to google yourself to find his nasty name. Absolutely rotten thing to do, and he did not say it like it was a thought, joke or an interesting idea. It was simply just a nasty rumor.
Marisa had played in good movies up until that point, and was (and is) well liked. But there is no doubt that this caused her to not benefit from her Oscar win. She might have been better off not winning it frankly due to the nasty story.
Fortunately she is doing great today, getting a lot of attention for being Aunt May in Spider Man and getting great roles.
Thanks for reading: What Hollywood actor had a hard time getting work after his/her Oscar winning performance?, Sorry, my English is bad:)