What if Gandalf took the One Ring? Gandalf couldn’t have taken the ring because it would’ve been worse than Sauron.
So it would be implying that he could have good intentions at first, but the result would turn out to be more evil than good.
Gandalf’s Order as a Maia
As an emissary of the powers, and a creature of the same order – he was an immortal spirit in visible physical form. Much like Sauron, Gandalf was able to veil his power.
He and Sauron are part of the Maiar – the wisest of them all, with the name Olórin, and later Mithrandir (in the context of the Silmarillion). This meant that he had the same order as the Valar, but to a lesser degree.
As a Maia (pl. Maiar) he would be a servant and helper of the Valar. The Elves don’t know how many of them there were – but they were seldom visible in form to Elves and Men.
Gandalf dwelt in Lórien, but he often went to the House of Nienna and learned pity and patience from her. He was also called Mithrandir.
When the first shadows were felt in Mirkwood, there were the Istari – whom Men called the Wizards.
Mithrandir was the most vigilant and he doubted the darkness in Mirkwood. Out of Radagast, Curunír and himself – Mithrandir was closest in counsel with Elrond and the Elves. (Cúrunir was Saruman the White.)
Gandalf had feared the first shadow of Sauron returning, and went to Dol Guldur. There was finally some peace for a while, however the Shadow returned and power increased, for a second time.
By then, the Council of the Wise had occurred consisting of Mithrandir and Curunír, along with Galadriel, Círdan and Elrond and other lords of the Eldar.
Additionally, Saruman had started learning about the Rings of Power, and the history.
As the shadow grew, the hearts of Elrond and Mithrandir had darkened. They realize that Sauron himself had taken shape again and was growing and trying to gather all the Rings to his hand.
Gandalf figured that with more power he could master the Enemy.
The Wise were troubled – but none were as perceived by Saruman the White – who went against the swift deeds to master Sauron suggested by Gandalf.
By then, Curunír had turned to dark thoughts and became a traitor. He did not want anyone finding the Great Ring, and started envying Sauron and wanting the Ring.
Mithrandir spoke to the council after a while – saying:
“It is not needed that the Ring should be found, for while it abides on earth and is not unmade, still the power that it holds will live, and Sauron will grow and have hope. The might of the Elves and the Elf-friends is less now than of old. Soon he will be too strong for you, even without the Great Ring; for he rules the Nine, and of the Seven he has recovered three. We must strike.”JRR Tolkien, The Silmarillion “Of the Rings of Power”
Curunír assented – desiring Sauron to be thrust from Dol Guldur. He aided the council for the last time and Dol Guldur was assailed. But it was too late, and Sauron had seen it.
War of the Ring
After Gandalf first learned of the Ring, Sauron was dismayed – and in the last battle consisting of himself, as well as the sons of Elrond, the King of Rohan, and the lords of Gondor, and the Heir of Isildur with the Dúnedain of the North – they had looked upon death and defeat and Sauron was too strong.
Sauron had believed that the Ring was destroyed by the Elves – but continued seeking it after he found out it was indeed not destroyed and the ring was taken from him – as the strength of the Elves to resist him was greater before, but not all Men were estranged from them.
Gil-galad, Elven-king and Elendil of Westernesse overthrew Sauron eventually, during which they had perished – for the Men of Westernesse came to their aid.
It was later lost and fell into the Great River, Anduin, and vanished after Isildur married north along the east banks of the River. Isildur was killed when the Orcs saw him and the Ring slipped from his finger as he swam one day.
However, the Periannath (hobbits) were able to bring them deliverance. While all were achieved with the guidance of Gandalf – who was revealed as a lord of great reverence, the Heir of Isildur have taken up their lordship of Men, the power of the Three Rings has faded and the world grew old and grey – and thus, the last of the Elves left Middle-earth to go to the Undying Lands. And lastly…
One can imagine the scene in which Gandalf, say, was placed in such a position. It would be a delicate balance. On one side the true allegiance of the Ring to Sauron; on the other superior strength because Sauron was not actually in possession, and perhaps also because he was weakened by long corruption and expenditure of will in dominating inferiors. If Gandalf proved the victor, the result would have been for Sauron the same as the destruction of the Ring; for him it would have been destroyed, taken from him for ever. But the Ring and all its works would have endured. It would have been the master in the end. (JRR Tolkien, Letter # 246)
And in a draft, he writes: Gandalf would have made good detestable and seem evil.
[…] Mithrandir was the most vigilant and he doubted the darkness in Mirkwood. Out of Radagast, Curunír and himself – Mithrandir was closest in counsel with Elrond and the Elves. (Cúrunir was Saruman the White.) – this would later be known as the White Council, or Council of the Wise. […]