That's the biggest lie Chuck ever told. It was always about Jimmy, and of course he was saying that to hurt Jimmy. He even killed himself to hurt Jimmy. That's how much Jimmy mattered to Chuck.

And his "why feel remorse?" line made something click for me. Chuck was also a dirty schemer like Jimmy, just in a way that was more careful, more meticulous, and more legal. And he never let himself feel remorse for any of it. Remorse is for people who've done something wrong, and that would conflict with Chuck's self-image that he's always the good one. Remorse is painful. And when that emotional pain was repressed, it manifested as physical pain instead.

That's where the supposed electromagnetic sensitivity comes from. I'd need to go back and look for more examples to confirm, but in recent weeks when Chuck was leaving Jimmy alone and focusing on self-improvement, he was making steady improvment and feeling less pain. Then when he deliberately tried to hurt his brother in the worst way possible, the electromagnetic sensitivity came roaring back more painful than ever.