Alas, Poor Villain: Kaibutsu, who is revealed to look and behave like he does because he was tortured for 5 years by humans using him for scientific experiments.
Anvilicious: Oh boy... don't let me get started on Weed and his morals...
Damsel Scrappy: Many fans dislike Reika for her role of "Just There" in the anime/manga and getting kidnapped.
Germans Love David Hasselhoff: Much like its predecessor, the serie recieved more attention in Scandinavia and Finland than any other place.
George is one of the favourite characters among the manga readers. He isn't in the anime. This is just another thing that made the fans unhappy.
Tesshin is also an example of this. Apparently, he's very popular with Japanese readers.
Unfortunate Implications: Near the end of the manga, many fans were unhappy at the idea of Weed and Koyuki mating and having puppies. Even though they are dogs, it has an unpleasant parallel to the implications of teenage pregnancy as both Weed and Koyuki are too young to become parents.