Hero or Villain?

This is a question I've been asking myself a lot recently, in regards to the mc of my first novel, Ares Pyrrhus.

Ok first off I'll give some background info on Ares. He's a demi-god. Demi-gods in my world (at least the ones that are half human and half god) can live around five hundred years. His mom is Raze, goddess of creation and destruction, and his father is Lonan, a disciple of the god of chaos. He raised an army and pretty much killed everything in his path. Its considered taboo to even say Lonan's name, so most people just call him the knight of chaos.

One day Lonan lauched an attack against the small kingdom of Convallis. The king of Convallis hired a famous mercenary, Celerus. Both Celerus and Lonan intrigued Raze, so she decided to mate with who ever won the battle between them. However, they killed each other during the battle. So Raze decided to mate with both of them. A god mates with a mortal by taking a part of the mortals soul and mixing it with a part of their own soul. The union of her and Lonan created a baby boy named Ares, and the union of Raze and Celerus created a baby girl named Celes.

She gave Ares to his grandparents to raise in a small village. Around the age of eight, the village was attacked by slavers and Ares'es grandparents were killed. He was taken as a slave. He was quickly sold to the leader of a crime syndicate. He served his master for three years. One day he killed his master. While escaping he came across a female half-elf slave that was a year younger than him. He had heard some of the members of the syndicate brag about raping a young half-elf and he figured that it was her. He convinced her to escape with him. He promises her that he'll protect her. Over time they fall in love (brother-sister kind of love, not boyfriend-girlfriend kind of love). They live in an abandoned house and steal whatever they need to survive.

As they get into their late teens they become skilled with weapons and become assassins. During this time, Ares realized that he likes to kill people and enjoyes it when someone he hates fears him. After being an assassin for a few years he realizes how corrupt some of the goverments are so he decides that he'll destroy all of the nations and syndicates on the continent of Xen and rule it as its emperor.

As for his appearance and mannerisms. Ares is five foot, nine inches tall. He has a very lean build. He has black hair that goes down to his shoulders and a tattoo of a dragon that goes around his left arm. He wears that black cloak that hides much of his appearance. Due to a family trait that he inherited from his father, his eyes are red with a slit pupil (similar to a cat). He is friendly and loyal to his friends. However he is cruel and merciless to his enemies. He is intelligent and can move at incredible speed. He is not very strong. He fights using two silver daggers and six black throwing knives.

The case for him being a hero is that some of the people really are better off with him around. He starts to raise his army by killing slavers and freeing the slaves that they once owned. For the chance of creating a world without slavery and a world where their children and grandchildren could have a chance at happiness, the freed slaves give Ares there absolute loyalty. Some of them even sees Ares as a savoir. Also in some of the nations of Xen, only children from rich, land owning families can go to school. Ares creates public education. Also Ares belives that advancement in the military shouldn't be based off of what your last name is. Due to this, many soldiers from nations that he conquers joins him. He is also very loyal to his friends. So overall, society as a whole is better off under his leadership.

The case for him being a villain is simple. He is incredible sadistic. He loves to torture, kill and create fear among his enemies. As an assassin he killed people that did nothing wrong other than pissing off the wrong person. He even has a couple of psychotic breakdowns during his life, where he just killes everything in sight. He believes that the strong will always rule over the weak. Also some of the nations that he goes to war with, had peaceful and happy people. These nations did nothing wrong other than being in the way of his ambition.

So I'm not sure whether I should classify him as an anti-hero or as a noble villian.