What is the worst anime for you?
For me it has to be a toss-up between Gantaz and Death Note.
Death Note is simply awful because you have an extremely OP character who is incredible on so many levels and never actually loses and his 'rival' or whatever is obviously better but because our main character is the star, the rival gets diluted and dumbed down as to not overshadow our star.
But Gantz takes it.....A character basically gets raped(or almost raped) every episode, the main guy is incredibly annoying and perverted and sickening. And pretty much all the characters except his friend(the muscular guy with some issues) have zero depth