It is said in *Of The Rings of Power and the Third Age* that Sauron did the bare minimum to avoid punishment after the War of Wrath: “When Thangorodrim was broken and Morgoth overthrown, Sauron put on his fair hue again and did obeisance to Eonwe, the herald of Manwe, and abjured all his evil deeds.
In The Silmarillion, Tolkien tells us about this brief period, in which Sauron was regretful of his servitude precisely for knowing the fate of Morgoth and wanting to avoid it for himself.
Later on, when Morgoth was finally defeated and banished into the Timeless Void during the War of Wrath, Sauron briefly repented and went to Eönwë asking forgiveness so that he wouldn't face punishment by the Valar, but Eönwë told him that he would have to face Manwë's judgment.
He quite clearly says that he is repentant, and he is ashamed. He says it in The Silmarillion, and he says it in some notes in Morgoth's Ring. But he always puts the words "out of fear" right after "repentance." I think fear can lead one to genuine repentance, and I think he fears the gods and he fears retribution.
Sauron did not truly repent. He saw the might and power of the armies of the West and he was afraid. He saw them defeat and force Morgoth into the Void, and Morgoth was his chosen leader! The one he had known to be powerful, more powerful even than most of the Valar.
Sauron's deepest fear was that Aragorn would use the Ring against him. With its powers of domination, Aragorn could comfortably take over the entirety of Sauron's dark army. Though this would eventually corrupt Aragorn, it would allow him to destroy Sauron and take his place.
Sauron seemed to genuinely feel a connection to her, and part of that came from sensing the darkness inside of Galadriel. In that regard, his offer was really a seduction to the dark side.
Thus, Galadriel's dark form in Jackson's The Lord of the Rings personified what would have occurred had the Lady of Lothlorien given in to temptation and taken the One Ring for herself. She would have succumbed to evil because the Ring was indomitable, even with her power.
"So I think in his pitch to Galadriel, it cannot mean that he loves her or that there's any kind of romantic relationship. There should be no ambiguity around the fact that Sauron is evil — he's terrible, and he's using Galadriel to enhance his power."
"Sauron was 'greater', effectively, in the Second Age than Morgoth at the end of the First. Why? Because, though he was far smaller by natural stature, he had not yet fallen so low. Eventually he also squandered his power (of being) in the endeavour to gain control of others.
Melkor is the most powerful of the Valar but he turns to darkness and is renamed Morgoth, the primary antagonist of Arda. All evil in the world of Middle-earth ultimately stems from him. One of the Maiar of Aulë betrays his kind and becomes Morgoth's principal lieutenant and successor, Sauron.
He will fight in the Last Battle against the Valar and their allies, but will ultimately be slain by Túrin Turambar, the Man he cursed. By finally defeating Morgoth, Túrin will avenge not only himself, but all members of the race of Men.
When Halbrand and Galadriel captured Adar, Adar seemed not to recognize Halbrand as Sauron. Adar also claimed to have killed Sauron after watching Sauron experiment on the orcs, whom Adar sees as his children. It's possible Adar was pretending not to recognize Sauron as part of a ruse.
In order to make such a weapon, the crafter themself would need to be just as corrupt and be able to provide some of their life force to keep it powered. So unless an equally evil being held the same ring-making knowledge as Sauron, it was impossible to make another.
Additionally, while he was in his weakened state, Galadriel could hold him off through the power of will alone. However, if Sauron had his One Ring and faced off in a battle against Galadriel, it's unlikely that there would be much she could do.
Morgoth, the first to reign terror upon Middle-earth, was more powerful than Sauron and commanded an army of dragons and Balrogs. While both Morgoth and Sauron were cunning, Morgoth's rule and terror lasted longer and his corruption spread further, making him more formidable in the Lord of the Rings universe.
In the final minutes, Sauron confesses that he's been manipulating Galadriel since they first met — using her as a way to get back to Middle-earth to fight back against his enemies in the Southlands and indirectly form the land of Mordor but also to get closer to Celebrimbor and the Elven smiths.
Sauron's only interest was an order or to work upon the world in an orderly state, even in the beginning, Mairon really had no love interest. Despite his deceptive attributes, he was a trickster and a seducer, he had little care for attempting to love someone.
In his notes, Tolkien remarks that Sauron saw Galadriel as his equal. Add that to the fact that she's untrusting of Sauron (yes, even when he's in his Annatar guise) and an unwavering, single-minded force, and it's more likely than not that Sauron feared Galadriel — or the potential she held to upend his plans.
For those that haven't read Tolkien's work, it's easy to see why many audiences suspect Gandalf and Galadriel are in love. After all, many of their interactions in The Hobbit trilogy practically scream romance. However, their relationship remains purely platonic in Tolkien's source material.
Sauron did not fear as we think of the word. He was very cautious of the men of Numenor and the remaining Noldor in exile. No other force seemed to give him pause since the First Age. This was his undoing.
Take note, then, that at the root of Gandalf's quest is fear -fear of Sauron in particular. We are not told exactly why -but Sauron is a fellow Maiar, an angelic being who chose to follow Morgoth at the beginning.
In general Sauron did not seem to be afraid of the Balrog during the Third Age. The behavior of Durin's Bane indicated that he would not leave Moria and its tunnels : he was not a rival for the control of Middle-earth and the Balrog did not share Sauron's abilities as a potential Dark lord.
