The correct answer to this question is:
“That people found him weak and physically inadequate”
In the story, the protagonist Gegore Samsa actually depicts Kafka himself. Kafka's father always used to treat him as if he were garbage (just like Gegore’s father) to the point of making Franz feels like a bug. This made him feel so weak that there is nothing he can do to stop the abuses done to him.
One of Karfka’s fear was to his father, this influenced work as “A Letter to My Father”, “The Judgment” and “The Metamorphosis”, his relationship with his father was complicated and tense, he did not like the majority of his paternal family, his father disapproved his work as writer, all this issues led him to decreased self-confidence.
