Wait! I can actually answer this one,it is by a long shot Master of Martial Hearts which is a 5 episode straight-to-DVD OVA knock-off of the concept from Ikki Tousen made far,far worse. The stupid nature of the show is readily apparent from the word go when you realize it's one of those fighting girl series where every punch and kick sunders ridiculous amounts of the target's clothing,what you won't see coming though is the ending. The ending to this series is such a mean spirited,out-of-place,and completely mind-boggling stupid shift of tone that it will buttfuck your brain ala School Days.If you must know more then perhaps you would be interested in JesuOtaku's review of it over at ThatGuyWithTheGlasses. I wouldn't actually recommend it though because the scenes from School Days' ending used as a parallel to this one were enough to ruin my week.If you haven't seen it then how can you claim it in a list of the worst anime you've seen? I can imagine that trying to insert an ICBM into my anus is probably a terrible idea but that hardly qualifies me to list it as the worst thing I've ever done.I want to rectify this decision of yours by noting that I've seen Green Green myself. It's not bad so much as it is shallow and stupid. Green Green is what the American Pie movies would've have been if they'd been made in Japan. It's tits and slapstick sexual humor. The developers completely forget the plot until the last three episodes and the bonus episode is just a softcore hentai that I personally deemed non-canon the moment I saw it. It never tries to be anything more complex than that and I bothered to watch it twice. Then again,I watched Ichigo Mashimaro twice and that series makes me feel like a pedophile. Probably for a good reason.
I heard Green Green is bad.