If we’re counting the SEs then I guess the worst moment in all of the Star Wars movies that I’ve seen is the dance number in Jabba’s palace. Not including the SEs I’d probably say the CGI Peter Cushing stuff in Rogue One. Either that or my initial choice of the droid assembly line in Clones.
Worse than Jabba in Star Wars? The new song and dance number might be more cringe inducing, but Jabba in Star Wars has implications for the viewer that stretch beyond the single scene and even movie.