Satan

Satan is depicted as a large, muscular, red dragon-like demon with four eyes and horns. He wears a black and red leather jacket and black pants adorned with an orange skull belt. Orange lava streaks can be seen on his wings, neck, and left arm, while the other is red. His two outer horns are black and red stripes, while his two inner horns are black and white, and are positioned in a manner resembling a pitchfork. He also has a large red and orange tail with spikes coming out of his back.

Satan is shown to be a very hot-tempered demon with anger issues and fits of rage that leave him out of control and he needs a demonic therapist to act as a "shoulder angel" to remind him to stay calm. Despite this, he can also be reasonable and sophisticated most of the time.

He is shown to have little to no care for the demons below him in Hell's hierarchy, especially the Imps despite claiming to be their creator. To him, the Imps (and most likely the Hellborn and other Hellborn mortals) are nothing more than pawns that only serve to obey orders and do his job.
Not even real demons escape his indifference, despite holding them in much higher regard.
Satan is also shown to be immensely vain and arrogant and revels in his position as the leader of the Deadly Sins in Lucifer's absence. Despite the fact that Hell was created after Lucifer granted humanity free will and was cast there by Heaven to rule over it, Satan proclaims himself to be the original ruler. Due to the absence of Lucifer and his family from the affairs of Hell, it would seem that this claim of his has become a reality for the rest of the Hell-born demon race, save for his fellow Sins (at least Asmodeus and Beelzebub), who know the truth about who is really in charge.

Skills
Longevity: As one of the deadly sins, Satan shares the longevity of his fellow sinners.
Flight: Satan can fly with his giant dragon wings.
Environmental Manipulation: Satan can warp the colors, mood, and lighting of every room and palace he is in, as shown when Satan interrupts Stolas' musical number and the courtroom turns a yellow-orange color.
Pyrokinesis: As shown in his song , Satan is able to create images out of flames, such as the image of an angel. The smoke he emits from his nostrils when he is angry may suggest that he can also breathe fire.
Power Disabling: Satan, with the use of an enchanted set of rings bearing the sigils of the Seven Deadly Sins, can strip high-ranking demons of their powers and status. He performed this on Stolas and set him up for one hundred years for providing the grimoire to Blitzo.
Enhanced Strength: Due to his size, Satan seemingly possesses incredible physical strength, such as being able to shatter the ground when he stomps.

Leadership: As the de facto leader of the Seven Deadly Sins and the rest of Hell, Satan has a strong sense of command within his government, with the other sins trusting him with their authority. He is also incredibly intimidating compared to the other sins, to the point where even high-ranking Hell-born species are afraid of displeasing him if they step out of line.