I agree, school days was actually really good for what it was trying to accomplish; It wasn't listed as a ROCO, but a tragedy and i think it fulfilled that purpose to the extreme. Its one of the few anime's that to this day still make me cringe, which says something vs the 100's that i have completely forgotten about.
As for the worst things; Revolutionary Girl Utena sticks out; I watched it because back in the day it had a rule to watch a series to completion regardless of how bad i thought it was. That was the series that changed my mind; To this day i dont know why people still thinks it was a good anime. Bottle Fairies was the first one where i got 2 eps in and said 'oh hell no' and moved on.
I actually liked school days as well. It made me hate Makoto for the perverted, manipulative POS that he was but it really did set out what it wanted to do and it did it in spades. It also felt like a breath of fresh air compared to many other series that would just end up as normal harem romantic drama. I like that it was distinct in what it did.
Boku no pico
One Room was completely terrible. To this day I still have no idea why I ended up watching every episode.
The worst I've ever completed is Pupa. I'm not really disturbed by it or anything, I just hate it from a critical standpoint. The "horror" entirely relies on the shock of siblings cannibalizing each other, which I wasn't really all that shocked by... The plot was boring, the art was ugly, there were too many loose ends. All in all, it was terrible. 2/10.
Now, the worst I've ever watched (but didn't complete) is Eiken. The art is ugly, the animation is horrid, the plot is non-existent, the characters are stupid and terrible, and my intelligence was greatly insulted by this piece of sh#t. I fell to a nearly vegetative state while watching it. The actual main reason why I never completed it was because the second episode was downloaded incorrectly and cut out after a few minutes. I took it as the universe telling me that I didn't need to suffer anymore, and never watched that second episode. 1/10
Pupa the anime is fucking garbage, I kept up wiith the manga until they decided to stop translating it. Also you can't really expect much when the episodes are like 2 minutes long?
Battle programmer shirase. LOL what a waste of time. It had potential it was so shitty it got cancelled midway.
Well, from what I read, I've been saved from a lot of titles... That you guys mentioned.
Made me wonder if I ever saw anything bad (also, because it's the topic)
Vampire Knight, I guess. Seemed a cliché ending. Barely remember it but left a sour taste.
Felt bad for SoulEater, Capcom disappointed me even though they did a great job with it's animation.
School Days was macabre and it did it's job well done.
Worst anime for me was Skip Beat.
Bleach :/ I really loved it when it came out. Fell in love with character designs. The story was just bad in my opinion it felt so repetitive watching a new arc felt like a chore.