Ganondorf's face is hilarious, but also frightening at the same time for a very particular reason. Notice he only starts laughing when he witnesses how much pain his actions have caused Zelda. He likely wasn't even counting on the actual Zelda being present, and getting to see her suffering firsthand fills him with such joy that he can't help but genuinely smile and laugh.
A lot of people claiming it was a stab, but with the sound effect I find it way more interesting that he just murdered her with a punch. You can even see her head jerk back from the force.
Well for someone as big as him and with the strength he had and how well-built he is of course a single punch from the back can break someone's spine which is really lethal
There's like three reactions in this one scene - Fake "Zelda" throwing the knife - Sonia gets punched/stabbed - That Ganon face 1:16 oh look there I am
People laugh at the face Ganondorf makes Meanwhile my brother and I got chils from that face because we were reminded of his chilling laugh from Wind Waker 😬