can anyone tell me why Dobey hates the family(Malfoys) that he serves?

Dobby was treated badly দ্বারা the Malfoys so he was আরো likely to disagree with their values and be against them and their beliefs. On the other hand, Kreacher was treated well দ্বারা the Blacks, especially দ্বারা Regulus.

Well Dobby is always getting hit দ্বারা Lucius and his cane. They always mistreated Dobby.
While Kreacher loved his family and Sirius's mother a whole lot he looked up to her. But the weird thing about him is that he wants his head up in a row with his mother অথবা something but he liked his life.