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He's had a stroke that cost him the full use of his right arm, leg and possibly his eye too. Aside from the visor, bulbapedo points out his in game sprite shows him not moving the right side of his mouth, we don't see his right arm because he goes out of his way to hide it, he walk slower a few times although be shown at normal speeds and by BW2 he's degraded to the point that he needs the staff as a cane.
He was physically insanely strong before getting fucked up by either a stroke or his hydreigon to the point that he's become unable to maintain that physicality
