Seth’s a lot of things. He’s a wild storm that can blow back invaders or can cause destruction for inhabitants who wrong him.
He’s a great lover but he’s also an avenger. (many wives / smites a/phofis and attacks enemies of egypt)
It’s more like…accepting a complex figure. I don’t think he’s evil. Obviously. I know from academics and historical primary sources that in the old ages – before middle kingdom, new kingdom and especially the graeco-egyptian era, he was highly benevolent.
He protected Egypt against invaders coming from the sea, had healing qualities, ect.
Many other egyptologists here and there agree- he’s not as evil as he’s painted out to be.
“…there is no real Devil in Egyptian theology. Set, the murdere of Osiris, was only evil in specific contexts. He represented the barren desert and the storm, forces of disorder, but he could sometimes be personable and agreeable, holding the ladder for the dead king to mount to heaven and helping Re repel the threatening Serpent. ”
Red Land Black Land
So I guess for your answer, he’s not just evil and good. He’s a complex character, but then again these gods are anthromorpic – meaning they are like humans in some ways. This case being his complex personality.
But what I can tell you is this, despite killing Osiris, in most myths before greek intervention or periods where he fell out of favor (with invaders associating theirselves with Set, pissing the native egyptians off) he was beloved. He protects Ma’at, rides with Re as he is the only one strong enough to smite a/phofis daily.
We have art of men who desired to be close to him, he was their patron and they felt honored to be named after him. (Stele of Aapathey)
Kings honored him (early ones and then the seti family). He was – and still is a friend to the dead.
I know this is probably not the answer you wanted, but it’s not black and white. It’s a little more complicated than that. The way I see it is that, for example, the killing of Osiris was both bad and good – it was murder, but Osiris was known to torture Seth and struggled to deal with Re’s power in the form of the crown. When he’s killed, it’s mentioned he’s purified. (BOTD texts)
Seth, in some cases with Thoth, is mentioned weeping for Osiris. Also, as some scholars note (I believe I posted something with this, you might have to dig through my archive) that seth started the cycle for kings. Life, death, succession, repeat.