Sidious' lighting fatally wounded him after a couple seconds of hitting him but Luke was hit by it much longer and survived. That seems like a weakness to me.
Dude, sidious was toying with luke, he amped his lightning to its max level v vader and aimed the lightning at vader's skull, luke was out performed by vader there.
It looks like Sidious just accidentally hit Vader with the lighting to me. Sidious was just freaking out and he kept shooting his lighting on his way down too.
Sidious' lighting fatally wounded him after a couple seconds of hitting him but Luke was hit by it much longer and survived. That seems like a weakness to me.
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