Hurting someone you love.

A scorp male friend of mine admited something to me that didnt make sense to me atall.He said he likes to hurt those he love.Every body sees his good part but the one he love had to deal with bad him,he said he has been meanest to the girl he loved most.
I know him since many years and i know he as a amazing friend and a good human being but to her he has not been good but still cailms to love her.Is it possible to delibrately hurt some one you love?Anmd if yes why do you need to do such a thing?