Nemesis, because it was the prime continuity committing suicide. Watching it in the theater was like watching a train wreck in slow motion. And then it flopped.
I remember being excited to go watch it. I was even spouting off to my coworkers at the time "I'm going to watch Nemesis! It's going to be kick ass!" Went with a good friend from work.
Then I saw it and slowly it became stupider and stupider.
"Why is there a damn dune buggy with wheels in this movie?"
"Does it use gasoline? so you know, you get the full nostalgic effect of driving an ancient vehicle"
"Where are the fucking Romulans? I was promised mother fucking Romulans! All I see is fucking vampires!"
"Why does B4 sound like he's got a broomstick up his ass?"
"Why is the goddamn set so dark?"
"Why is the Andromeda Ascendant showing up in a Star Trek movie? oh wait, it's the "Schimitar" and it's got a gazillion torpedo launchers and twice as many phaser banks, and like 8 layered shields
And just kept getting progressively worse. Then Data died and I felt like I got kicked in the balls, and everyone was fucking depressed, and the entire movie ended this way.
My buddy goes to me "wow, next week when LOTR - 2 Towers comes out, this movie will disappear completely off the radar"
And he was right. When LOTR came out a week later, Nemesis was done.