Satan

Satan is one of the Seven Deadly Sins, embodying the Sin of Wrath. Satan became the stand-in leader of the Sins and ruler of affairs in Hell. Matching the sin he represents, Satan is shown to be a very wrathful demon with anger issues and fits of rage which left him out of control. His uncontrollable rage is too much to the point that he needs a demon therapist to act like a "shoulder angel" to remind him to keep calm. Despite this, he can also be reasoned and well-sophisticated most of the time. Satan is also shown as being immensely vain and arrogant and revel on his position as leader of the Deadly Sins in Lucifer's absence. Despite the fact Hell was created after Lucifer bestowed free will to humanity and was casted there by Heaven to rule it, Satan self-proclaims himself as being the original ruler. Due to the absence of Lucifer and his family in the affairs of Hell, it would appear that this claim of his has become a reality to the rest of hellborn demonkind, except for his fellow Sins (or at least, Asmodeus and Beelzebub), who know the truth about who is really in charge.