Oh man, that's kind of subjective. I'm pretty sure I probably don't remember the worst anime I've ever watched because it was probably so bland I can't remember but my vote goes for Yamazaki.
Like when you see something like ''Makoto-chan'' or ''Crayon Shin-chan'' you kind of forgive them because we've all met kids throughout our lives that are simply awful due to lack of atention, just like Arale from ''Dr. Slump'' kind of suffer from the same problem but it manifests in a different way.
But once you reach the later years of elementary school years and particularily when you reach 7th grade, you're supposed to grow out of that phase, and while still being kind of a pain in the neck at least you shouldn't still pretend to be hell incarnate.
That's where ''Gakkyu-oh Yamazaki'' (1997-98) comes into play, now I don't know if it was my age (I was always an old soul ever since I was like 8 years old) but I just couldn't stand the titular character's dastardly mean overall treacherous egotistical nastyness and his personal meastreatment and loathing to everyone else around him as if he was chosen by God to do so or something.
Like when you compare it to say ''Dotto! Koni-chan'', the main protagonist is the complete opposite to Yamazaki and you're soppossed to root for him and learn what not to do from the many characters that not only behave but are indeed awful but they get what they deserve in every episode, yet in Yamazaki's case, its the complete opposite, where the people who suffer at his expenses seldom get some reparations even when his plans are foiled, and not only does he succeeds every once in a while for I don't know what reason, but his wierd family always has nothing but praise him for him as if he was some sort of bizarro unsung hero.
And if he had been fully fledged as a villain such as Count Ludwig Presto Von Meinstein from ''Mon Colle Knights'', Horace from ''Cybot Robotchi'' or Etemon and Nanimon from ''Digimon Adventure'' I would've been fine with it, but he was always surrounded by good people portraying him as a force of good despite being awful to everyone.
I've heard there's a stereotype in Asia about a Chinese traditional folk hero named Goujin who is regarded as one of China's most beloved historic figures despite having come up with the most treacherous and nasty tactics in order to win his wars, so maybe that's the nuance I'm not getting from Yamazaki, but I hated the little bastard so much so to the point it made me feel sick from my stomach.
I'm still glad this was the only Anime that made me feel like that as opposed to so many American properties of the 90s and early 2000s.
