the difference between how Tai Lung looks at others (even if it's the god of kung fu) and how he looks at Shifu.
I mean, this scene is very revealing in that regard. Tai Lung does not even hide his arrogant condescension towards others, and his gaze from under half-closed eyelids emphasizes the point of view (He doesn't even try to feign any interest, lmao). but when it comes to Shifu, his gaze is open and he is completely focused on his father in search of support and reaction.
The boy grows up, he becomes bigger than anyone in the palace, and he still looks at his father as if he hung the moon.
and it is clear that after the betrayal of Shifu, who failed him in many ways, Tai Lung looks at him differently. and only when shifu manages to reach his heart, we manage to see for a few seconds not the formidable criminal who defeated the army on the way to his goal, but the little Tai Lung who most craved his father's approval and his pride.
but… It was too late and Tai Lung had gone too far to abandon the path that had caused him to lose decades.
Thank you for your attention, my magnifying glass and I will continue our work :)