What is the only thing Mufasa is afraid of in the movie "The Lion King"?

In The Lion King, the one thing Mufasa is afraid of is losing Simba. His fear is not presented as cowardice; it reflects the responsibility and emotional vulnerability of being a parent and king.

Mufasa is introduced as a powerful ruler who understands the dangers surrounding the Pride Lands. He teaches Simba about the circle of life, warns him to respect the boundaries of his kingdom, and repeatedly tries to keep him away from threats he does not yet understand. When Simba behaves recklessly, Mufasa's anger is usually rooted in concern for his son's safety rather than in a desire to control him.

The film makes this especially clear after Simba disobeys him and visits the elephant graveyard. Mufasa rescues Simba and explains that he is only brave when he has to be. In a later conversation, he admits that he was afraid he might lose his son, making the answer an explicit emotional truth in the story.

The wording can be confused with Mufasa's fear of Scar or the stampede, but those are dangers and conflicts, not the personal fear the question is asking about. The canonical quiz answer is losing Simba.