Another interesting way of viewing Mairon is from a time period standpoint and what he represents in that way. Yes the Lucifer analogy is great but have you ever thought about viewing him from a "consequences of war" perspective?
War makes people do terrible things, whether they are good people or bad people. Good people return from war as shells of their former selves after committing horrific war crimes under orders they cannot disobey. Bad people return from war even worse, having enjoyed their time committing atrocities.
And with Mairon, it's no different.
He joined Morgoth, became his Lieutenant, and began to slowly change from Mairon to Sauron with each action he took in Morgoth's name.
He gave up his ability to love or show love. He gave up his ability to understand other intelligent beings around him. He gave up empathy.
But when Morgoth was defeated, Mairon refused to beg for mercy at the feet of Manwë, electing to continue his rampage, going from good to bad to worse to evil. As nothing is evil in the beginning.
And he found that he quite enjoyed committing these war crimes freely, without Morgoth dictating how or when or why. And so, he fully became Sauron. No longer Mairon the Admirable, but Sauron The Abhorred. He gave into the temptation of going from the tormented to the tormenter. The tortured to the torturer.
And then, in all of his trauma, convinced himself that he was doing the right thing. Because he wasn't doing exactly what Morgoth did, no. In his mind, he was healing and perfecting, not destroying. But evil can only create things tainted with evil and malice. And as Morgoth created "Sauron", Sauron would go on to create more and more malice.
Sauron is not just an embodiment of evil, to some degree, but an embodiment of war atrocity.
In addition to what I've already said, Sauron is also an example of Tolkien's disdain for apartheid and colonisation. Sauron sought to colonise and enslave all of middle earth in order to "perfect" it and "purify" it. I don't even need to say the name of the dictators known for this behaviour for everyone to know who I'm alluding to.

















