It is theoretically possible that there are some long-forgotten Christmas movies, which are even more awful. But many fans are certain that Star Wars Holiday Special is the worst piece of Star Wars media ever put on screen, and quite possibly the worst piece of Star Wars media ever.
It is so objectively terrible, that it has been aired only once, in US just before Thanksgiving in 1978.
The Special was designed to keep Star Wars in the minds of the toy-buying kids, as audiences waited for The Empire Strikes Back, and a three-year span between episodes was feared to be too big at the time.
Thankfully, its creators were as wrong about that as they were about their ability to make a Christmas movie, while George Lucas and other talents behind Star Wars were primarily occupied with the troubled process of filming TESB.
George Lucas once said if he had time, he'd like to smash every copy left in the world with a sledgehammer.
In fact, he might have tried to actually do so, given that the versions available now on the Internet are unofficial recordings, captured by small TV stations across the US at the time of broadcast.
On the first glance a "Star Wars-themed Christmas movie hastily thrown together based on Lucas' drug trips" sounds like something that would at least be "so bad that it is good", a sort of badness that is either unintentionally funny or self-aware.
Unfortunately, Holiday Special is just bad. This story of Chewbacca and his family on "life day", an invented celebration of friendship and general niceness really has no redeeming traits. As one of the Reddit users said in a discussion of terrible Christmas movies:
"I knew it would be terrible, but nothing, NOTHING can prepare you for how inconceivably bad it is. I can safely say it is the worst piece of media that I have ever seen and will ever see. "
To give you an example of Holiday Special's badness which is not likely to tempt you into seeing something so spectacularly awful for yourself, it contains entire minutes of wordless grunting as the Wookiee actors try their best to communicate their family-friendly points with body language and animalistic noises while clad in stifling fur suits.
If anything positive can be said about Holiday Special, it is this: Holiday Special included the first canonical appearance of Boba Fett, the bounty hunter who would later obtain fan popularity disproportional to his relatively minor role and undignified death in the original trilogy, resulting in the Expanded Universe's writers spawning the entire Mandalorian culture around him.