Art the Clown is the main antagonist of the Terrifier series primarily portrayed by David Howard Thornton. Art is a sadistic, demonic clown whose only sole purpose is gruesomely massacring and maiming any in his way for no other reason than thinking it fun.
As far as the sociopath angle, I think Art meets most of the requirements. For one, superficial charm. One thing about Art is that he cannot talk whether it is because he chooses not to or is incapable is not known. But there are moments where Art can be oddly charming such as offering one of the girls in the first Terrifier film a plastic ring he got from a vending machine, or when he hands out candy to kids using a severed woman's head as the bowl. There are moments where he can be genuinely funny whenever he is not being murderous.
Then there is the grandiose sense of self-worth. One thing that comes to mind is the many times he commits a brutal murder, he writes his name like a painter illustrating their work. It is something he takes immense joy in and makes it a point to ensure people know he did this.
Art has a constant need for stimulation and can act impulsively whenever he is going in for the kill. Rather than just stabbing the person and being done with it, Art would instead find creative ways to prolong the suffering of his victims as long as he wanted and ensuring the experience the most excruciating pain.
And, naturally, Art lacks empathy or remorse for any of the many victims he has tortured and murdered. Or eaten chunks from. His relationship with the Little Pale Ghost Girl only amounts to them both loving blood shed.