hormone imbalance
Because some people are heartless .
heartless people
She is so heartless Only a truly heartless human being could treat puppies in such a cruel manner.
Not everybody on this planet like cats, y'know? Some people are just cold and heartless.
As the man walk away from the girl who loved him she she cryed, how could he be so heartless?
In KH 1, Ansem the Heartless leads them and Maleficent also leads them. In KH 2, the Organisation XIII and Maleficent can control the Heartless. When in KH 2 Sora asks on which side the Heartless are, Saix answers: "The Heartless ally with whoever's the strongest." So technically, the strongest leads the Heartless... I hope this helped ^_^
Heartless and jealous of them.
Because some people are cruel and heartless. Sometimes they may want to get money by selling their fur which is illegal!
They are Pureblood, meaning they are the original Heartless that weren't people missing hearts. They are monsters such as Darksides and Shadows that never needed a person without a Heart.
King Mickey told Ansem about Heartless, so Ansem was too intrigued to not look into them.
Do you mean how could you be so heartless? It's called Heartless, by Kanye West, if that's the one you're looking for.