anything but — not at all; far from being; definitely not

In the center of the frame, a teenage boy with spiky hair and a leather jacket sits quietly reading a thick book while his family watches TV. His parents and sister stare at him with surprised expressions, clearly expecting him to be loud or disruptive. The boy turns a page gently and adjusts his reading glasses with a peaceful smile. His family exchanges amazed glances as they realize their assumption about his "rebellious" appearance was completely wrong. that his behavior is anything but what his tough appearance suggested