Post an anime character who has two different personalities

Fukawa/Genosider or watever...

Lucy/nyu from Elfin Lied

Ukyo!! <33

Seijuurou Akashi from Kuroko no Basuke

Takashi Kawamura from Prince of Tennis....Despite his quiet personality, he becomes extremely aggressive and loud once he grabs his racket, or any racket. This change dramatic change is marked by him shouting "Burning!!!" "Great!!!" "Baby!" His personality along with these keywords when he holds a racket is most likely just for comic relief, but his personality change does have a large impact on his skills. While in his Burning Mode, he has a tendency to speak in English and to call people, mainly underclassmen, monkeys. Once in this persona Kawamura becomes filled with confidence and does not think before he speaks. He also sometimes refers to himself as "Ore-sama" (My magnificent self, The great I) during this phase.

Iori from Kokoro connect has many personalities.

Sakon (Naruto)

Hatsuharu Sohma from Fruits Basket

Shiro from Deadman Wonderland.

Train Heartnet from Black Cat.

He has one serious, impulsive, and vengeful side, while his other side is whiny, funny, and carefree.

Hazama or Yuuki Terumi Blazblue Alter Memories

Joker from alice in the country of hearts

No one else mentioned Moka??? I was gonna let someone else do it and then try to come up with someone different, but since no one else did, I will go ahead and post her. "When the rosary seal over her breast is removed, Moka's innocent self vanishes and her inner vampire… awakens." From Rosario + Vampire. I recently rewatched the whole show in a two day marathon and am currently reading the manga, trying to pick out the differences.