Post a picture of an Anime character who has a mental disorder...! Like ODC or something...

Nyu/Lucy from Elfen Lied she has Split personalities

Nice - Baccano!
She loves bombs, she LOVES to watch the explosions an the damage they cause, its like a high for her. i'd say thats pretty mental.

they dont say specifically that she does have one but

considering that she spent her childhood locked up in dark room treated like a test experiment and wasnt even given a name and then murdered an entire huge estate full of people id assume theres probably some mental issues going on there.

and on top of that she forced 10 year old riku to get her pregnant and then murdered him too... so yea. id say some mental problems.

Yagami Light - Superficially Charming

Sasori Akasuna
He has a mental problem with turning people into puppets. ._.

Multiple personality disorder...Sensui

Marik from Yu-gi-oh! I'm not sure if he really counts, but in a way he almost has multiple personalities, due to his own self and his "Marik" persona, if not him then Kaere/Kaede from Sayonara Zetsubou Sensei, she also has multiple personalities

Chihiro from ef a tale of memories can only remember things that happened in the last 13 hours.

link

Kid from Soul Eater he as a major OCD problem with Symmetry.

Ten Count (Manga) Shirotani (MC) He has OCD
I'll just use the cover, it's him in it anyways :D

Gemini Saga has split personalities.