Answer: Rued
Explanation: Rued is something that you feel sorrow over, A regret about an action that is done and wish it is not done.
“The movie star rued the day he did not return the telephone call from the studio head , as his career has declined steadily ever since”
It means the movie star regret not returning the studio head telephone call he missed as his career has been nosediving ever since then. Now he wished he had returned the studio head telephone call.