I don't think it's the worst ever, but the ending of Breathless (Jean-Luc Godard) is the first one that comes to mind and definitely one of the worst that I've watched recently - in spite of the movie not being bad.
[Edit] Many would disagree with me, by the way, but I just find it ridiculous and pretentious.
I'm not going to describe it; just take a look at it if you don't care about the movie or being spoiled.
I have periods of social disconnection, it's a part of me that I need and keenly embrace. I'll still log in and read news and threads during those times, but I won't be (very) active on the site, so I apologize for any inconvenience that this may cause (late answers, bumps or the like).
Please, feel free to correct my English.