A masterpiece of a series who's underlying theme is empathy.
Powerful, depressing, violent, and traumatic, it is certainly not for everyone, but those who feel such empathy for these characters will appreciate it's approach.
It has great writing, a fantastic English Dub that surpasses it's Japanese cast, with great pacing, and an approach that changes your perception once you've seen it.
Mamoru Kanbe masterfully crafts Lynn Okamoto's original story into a emotionally traumatic, and visceral experience that lets the view live in the moment, and ponder greatly long after the show is over about it's philosophical themes.
Elfen Lied is ever bit deserving of it's praises, and it remains one of the most powerful TV series ever made even 16 years later.
The criticism the series warrants is it's aging artwork, which one could dream of a company like KyotoAnimation taking the original frames and fixing the ones with low budget or poorly drawn elements.