Sam and Bilbo are the only people who ever willing gave up the ring after having worn it. ( well with a lot of persuasion in bilbos case, but he did decide to leave it to Frodo)
Neither Gandalf, Galadriel, Faramir nor Sam possessed it for any length of time.
Obviously it corrupted Sméagol greatly, more than anyone else. But he had it for a long time.
It also affected Bilbo, starting to make him feel “stretched-out and thin”, and tired. At one point Bilbo even called it “my precious” until Gandalf reprimanded him. A big reason why Bilbo left the Shire for Rivendell and gave it to Frodo was because he was afraid of what it was doing to him.
Frodo eventually started to give in to the ring at the end, claiming it for himself, but Gollum bit off Frodo’s finger before it fully took him over.
As far as I know, no one other than Sauron had the One Ring for as long as those people. Sam was tempted by the ring when he carried it, but he didn’t have it long and gave it back to Frodo later.
Understood, but again, you said nothing about possession. That’s why I believe your original statement was mistaken.
I didn’t think that was necessary. How else could it have corrupted them over time? Certainly not from afar. That’s pretty obvious. 
Did any of them put the ring on, or even own it? They just had a shot at getting it, iirc.
The Ring corrupted Boromir from a brief moment when he picked it up, iirc.
I don’t believe they did, no.
Rewatchibg The Return of he King and laughing at how Aragorn’s accent gets more and more posh.
Was Boromir corrupted by the ring, or by the idea of having the ring to defend Gondor?
Maybe it’s an argument of semantics, but I always thought of Boromir as not being “targeted” by the Ring, per se, but wanting the use the power of Ring to keep Gondor safe.
I always thought of that as how the ring got at him….
That’s why I called it an argument of semantics.
The power of the Ring would be tempting enough without the lure of the Ring along with it; even for those not bearing the Ring, it would represent a strong draw.
But there seemed to be something “more” to the Ring than just the attraction to power - probably part of the essence of Sauron as part of its makeup. I guess I would argue that Boromir’s attraction to the Ring is more mundane than mystical, whereas Gollum’s would be the opposite.
Isildur also seemed to have kept the One Ring (over Elrond and Cirdan’s objections) for similar reasons. He considered it compensation for the deaths of his dad and brother. He only had it for a couple of years before his death. (Sauron’s defeat and Isildur’s claim of the ring marked the beginning of the Third Age, and Isildur died in the second year of that age.)
One thing I have wondered:
Gandalf and Galadriel (and possibly Aragorn) were tempted by the idea of using the Ring’s power to overthrow Sauron. They resisted the temptation because they knew that the Ring would corrupt them, and the best they could hope for was to become Dark Lord, Version 3.0.
Was that ever a real possibility, or would the Ring have betrayed them, and they would inevitably become Ringwraith, Version 2?
Gandalf or Saruman absolutely would have become Dark Lord 3.0. I think Galadriel would likely have also. She was very powerful though not a Maia. In fact Jadis (the White Witch) of Narnia was apparently inspired by the idea of what if Galadriel seized the ring. Lewis & Tolkien were of course good friends back then.
Aragorn is tough to say. His innate power was far lesser than the other 3. It might have given him enough power to defeat Sauron this time but it would not destroy Sauron. So Aragorn would have lived extremely long and stretched thin as Bilbo put it. But I don’t think he would have become a Dark Lord 3.0. Perhaps a Wraith though. But once Sauron found a way to take back the Ring, Wraith Aragorn would either go insane or be ended I would think.
Would Sauron have killed a challenger, to make an example to the underlings, or would he have found it more amusing to enslave a would-be adversary?
I think the idea was that Sauron had poured so much of himself into the one ring that any near-peer with possession of it could have destroyed or at least subdued him with relative ease. Basically he put too many apples into one basket and gave himself an Achilles Heel. As long as he had the ring it made him more powerful than any normal peer, gave him eventual dominion over most of those less powerful than him (dwarves seemingly excepted) and if he was defeated but it survived, it preserved him from immediate destruction. But on the flip-side he was absolutely dependent on it and if a Saruman got his hands on it first, Sauron was fucked. Maybe short of it being destroyed Sauron would have still have survived as a diminished wraith or servant himself, but he wouldn’t be in the driver’s seat.
It would corrupt Saruman, slowly or quickly, but that wouldn’t be of much comfort to Sauron unless he could somehow engineer a counter-coup from an inferior position somewhere down the road.
And yet, after keeping the Ring for only that short a time, he already started calling it “precious” - which seems to be a marker of sorts for when the Ring really got its figurative hooks into its bearer. He also, in the same writing in Gondor, commented on the “great pain” it brought him - though that could have been due to the loss of his father and brother, now that I think of it.
It seems to me that - for any sufficiently ambitious entity - any of Sauron’s Rings of Power, especially the One Ring, presents an attraction solely as a tool for gaining or exercising more power. But there seems to be some kind of supernatural attachment that develops in anyone who bears a Ring for a while that goes above and beyond the basic attraction, particularly while the benefits of the Ring grow less and less salient over time.
I wonder if it’s because he was human.
Humans were the most vulnerable. Dwarves & Hobbits the most resistant. Sauron had almost no understanding of Dwarves and knew nothing about Hobbits. But he knew men really well.
That would also be why all the Nazgûl were human.
Well he helped make those 9 specific rings for Mortal Men. The One Ring was his backdoor into controlling the Rings of Powers.