Ear Worm: Pipiru piru piru pipiru pi! Not only is this repeated in the theme song, it is chanted in a high, squeaky voice every time Dokuro is required to resurrect Sakura, who dies more than Kenny ever did.
Fan Disservice: Female fans of the first season went into season 1 expecting the girls to be comically sadistic dominatrixes, & instead found that they'd all been turned into submissive fanservice nymphos.
They Changed It, Now It Sucks: Season 1 was known for it's macabre humor & intense cartoon violence. Season 2 had none of that, opting instead for a Puni-Puni Poemi/Eikan/last episode of Excel Saga style harem fanservice where they try to see how far they could push it without turning it into an actual porn. On top of that, Dokuro's personality was totally different.
What an Idiot: When Sakura gets an opportunity to get rid of Dokuro forever and have his normal school life back where he's not tormented by his classmates or skewered by a mentally unstable angel presents itself, one would think he'd absolutely jump at the chance to take it. Hell, he even lampshades several of the cruel and unfair injustices she did to him that causes her to cry (though to be honest, not a single viewer felt any sympathy towards her) and believe she's not wanted. Unfortunately, Sakura doesn't want her to leave and basically says that he doesn't mind all of the abuse as long as she's with him. It isn't a stretch to say that no one in their right mind would have chosen to do what he did.