When the Devil Gene completely takes over jin's mind, he becomes a crazed, aggressive, destructive and brooding devil. 

More accurately, Devil Jin can be treated more like the Devil Gene itself within Jin's body, with Devil Jin looking down on his host as someone weak-willed and insignificant.

Devil Jin seeks to acquire ultimate power and will do whatever it takes to achieve it. He is also very confrontational and sadistic, as he has a habit of laughing at the suffering of his foes during his win animations.