I can’t decide on the worst scene in the saga, so I’ll do one for each film.

Star Wars: Special Edition Mos Eisley. Completely cluttered with CGI comic relief.
The Empire Strikes Back: The giant worm cave. Serves no purpose story-wise.
Return of the Jedi: Jedi Rocks. Made me want to rip my eyes out and jam them into my ears.
The Phantom Menace: The podrace. Even more CGI comic relief.
Attack of the Clones: Battle droid Threepio. Would be okay if he didn’t spout bad puns constantly.
Revenge of the Sith: The opening scene. Cheesy and full of terrible comedy.
The Force Awakens: The battle above Starkiller Base. A lazy rehash of Star Wars’ climax.
Rogue One: Bor Gullet. Weird for the sake of being weird.
The Last Jedi: The ships running out of fuel. Only happens because they couldn’t rip off ESB without it.
Solo: Han getting his last name from an Imperial Officer. Contrived and pointless.