Joffrey was strong-willed as a child and had an uncontrollable temper like his mother's and an unchecked sadistic streak. He had little sense of right or wrong, which often leads him to trouble, especially when he loses his temper, and when things go wrong, he always blames the problems on others.

Why is Joffrey so crazy?

Perhaps it's only the Targaryens, but as they're known to marry sister to brother, it seems that this is a result of incest. Jamie and Cersei are full siblings, and twins at that. That Joffrey is a son born of incest could have caused his madness. Tommen and Myrcella just got lucky on that coin flip.

Who is more cruel Joffrey or Ramsay?

Ramsay is clearly terrifying and far more brutal than Joffrey, particularly in his season 5 marriage to Sansa. When Joffrey and Sansa were betrothed, he implied brutality toward her and psychologically tortured her, but when it came to physical cruelty, Joffrey always had one of his guards commit the acts.