I think there is a tie between 'Catwoman' and 'Green Lantern'
Batman and Robin. That was horrible beyond horrible. FWIW, I didn't see Catwoman, but Batman and Robin makes GL look like a masterpiece. Superman Returns had some good moments, but at the end of the film, we're all saying 'Who was that guy in the red cape? Because he sure didn't act like Superman."
Considering what was expected of it, Green Lantern really takes the prize. Like, it was meant to be the launch pad for a DCCU, the DC Iron Man that would lead to Avengers, and it ended in a big time flaming failure.
Batman and Robin is probably the worse movie, but considering you had Batman Forever come before it, you should have known beforehand which way the Tim Burton boat was heading.
As for Catwoman... well it's a spinoff from a non-existent movie and so far removed from the source it's best equated to Blade: The Daywalker back when Marvel had no faith in movies... and nearly backrupt.
And Jonah Hex... from the parts of it I've seen, it's not that bad (as I have no ties to the comic version), kinda like the first Ghost Rider. Stupid, but in an amusing and entertaining fashion.
Well, there is no DCCU by now. Pretty much all DC movies, with exception of early Superman and then Batman’s films, are separated/stand-alone.
Worst, I would say, is Catwoman. That’s wasn’t movie, that was utter waste of time and money.
I don’t really understand all that hate to Green Lantern movie. It’s mediocre, true, but watchable.
Batman and Robin… I always thought that was comedy/spin-off of 60-th Batman. Say what you want but that was fun to watch.