I really like 헤타리아 but from just recently, a lot of people have been saying that 헤타리아 was the worst 아니메 created. I'm sorry but I stand my ground and I 사랑 it :)
Zero no Tsukaima. I don't know anyone on 팬팝 who hates it, but almost every review on MyAnimelist about this 아니메 was negative, so I guess many people don't like it.