不肖
ふしょう unworthy (of one's father, teacher, etc.)
Why it means this
不 (not) + 肖 (resembling — a son should resemble his worthy father) — 'not living up to' one's father or teacher; a humble self-reference ('unworthy as I am', 不肖の身).
Breakdown
Each character links to its full entry — origin story, stroke order, and readings.