If InuYasha is the worst anime you've ever seen, consider yourself lucky.

For all the raves and praises and demands to see it I had thrown in my face over it, I'd have to say Neon Genesis Evangelion, even though Neon Genesis Evangelion is not a bad anime (and worth sitting through just to see The End of Evangelion alone). It's just terrible in comparison to all the praise it gets.

The single worst series I can remember sitting through and afterward saying "I want my wasted time back" would have to be Steel Angel Kurumi 2.0. That series was such crap, and especially made me mad after the first Steel Angel Kurumi was such a lovable series.