I prefer Anakin’s Dark Deeds. For Obi-Wan this is not yet “omg it’s Darth Vader bum bum bum buh buh-bum, buh buh-bum,” but rather whatever Anakin has turned into. It harkens back to his moment with Padme in ROTS of reckoning with what Anakin has done.
Or… how would it perhaps go to start with Anakin’s Dark Deeds, but switch to the piano Imperial March when he begins killing people? (Maybe skipping into the main part of the theme without the preliminary percussive buildup.)