those puppy-killing bastards from Lucy's past who did not get a death deserving of their deeds, it was far too quick.

Lucy herself is a rather tragic character, a lot of her kills in her past were done simply because she knew no other way to solve her problems and killing just came easy for her due to her nature. I mean she killed at least 2 happy families because she wanted a place to stay while she was on the run from the orphanage, a group of onlookers and passer-bys at a festival due to a jealous rampage(this is partially Kohta's fault imo for lying to her, but then again, he had no idea that she was homicidal) and ultimately Kohta's father and sister, the latter's death being somewhat cringe-worthy as she got freaking bisected. Until Kohta finally knocked sense into her and then she finally feels remorse for all that she did because it was only then that she understood the magnitude of her actions. It's that kind of thing in the development of a character that I like and Elfen Lied is a really good series for character development... at least for Lucy in any case.

To me, it was a love story, I ignored most of the violence, I'm numb to it anyway. The relationship between Kouta and Lucy was heartbreaking, how Lucy was betrayed, how Kouta accepts her for who she is when everyone else hated her, and how they were friends as children and due to jealousy they were torn apart only to be reunited by fate later on.
And even then, Lucy was left out of everything, when Kouta and Lucy kissed, only to be separated *tears*... ;_;

also I hate how Kouta and his cousin end up together and have kids in the manga. ew. no.

Involving a puppy.

and the part where that little girl with the 20 something vectors saw her father and he did double suicide>.< I nearly cried>.<