Zig Zagged: Dikliss is a jerk due to his bad background; Velvet dislikes him at first, but comes to pity him and works on helping him become a better person. The two eventually bond, forming a true Love Triangle; however, Dikliss grows jealous of Kelvin and plots to get rid of him.
Averted: Prince Dikliss has his good and his bad points.
Enforced: The writers want to teach An Aesop that wealth does not automatically make people classy, gracious, or polite.
Invoked: Serpentus, Dikliss' Evil Chancellor, deliberately groomed him into a jerk as part of a plot to discredit the royal family.
Exploited: Prince Kelvin tricks Velvet's father into engaging her to Prince Dikless so that when he appears to save her from the unwanted marriage, Velvet will be grateful.
Serpentus deliberately avoided this, planning instead to make him into a puppet ruler — meaning he's more useful if he's well liked before taking the throne.
Princess Velvet runs away from home to avoid her forced marriage with Prince Dikliss, fully expecting him to be a jackass.
Discussed: "I wouldn't want to marry Dikliss, even though he is a prince. He's such a prick."
Conversed: "Man, Dikliss is a douchebag in this story. He's just like Prince Humperdink."
Deconstructed: Dikliss is unpleasant thanks to spending his whole life dealing with the Deadly Decadent Court, constantly manipulated by everyone around him and treated as little more than a convenient pawn; a means to an end. His Arranged Marriage to Velvet is just another instance of this, something he greatly resents and can't help thinking of whenever he sees her.
Reconstructed: ...He's still a prick, though, and Velvet doesn't want anything to do with him. Not when she has a nice guy like Kelvin around.