Yes, by feats and common interpretation in Tolkien's works, Radagast the Brown is generally considered the weakest and least effective of the five Istari (Wizards), primarily because he focused on nature (flora and fauna) rather than confronting the growing power of Sauron, failing in his main task, though he was a worthy Maia in his own domain. While powerful in his specific area of earth and animal magic, he lacked the direct power and focus on combat and wisdom shown by Gandalf and Saruman, who often dismissed him as simple.
Radagast had much less power and wisdom than Saruman or Gandalf. Gandalf esteemed him as "a worthy Wizard", but Saruman scorningly gave him the bynames "the Bird-tamer", "the Simple" and "the Fool". Radagast was "a master of shapes and changes of hue".
Radagast wouldn't fight the Balrog. He'd stuff all the animals in his cloak and run. He would have became Radaghast the Crispy and Pulverized. He didn't have the Secret Flame ring.
Gandalf says that Radagast is a great wizard in his own particular way, also calling him a kind-hearted individual enjoying the solitude of standing guard over the Greenwood forest and preferring the company of animals to that of Men.
Gandalf the White. Galadriel isn't near as powerful as the other two. Saruman was the more powerful of Gandalf and himself, but after his fall and Gandalf's return, the God of Middle-earth allowed Gandalf to use more of his inner Maiar strength to compensate for Saruman's turn.
Voldemort quickly became feared so much that the majority of the wizarding world would not even speak his name, with most flinching when they heard it, and instead referred to him as "You-Know-Who", “He-Who-Must-Not-Be-Named” or simply “The Dark Lord”.
There were said to be Five Wizards, of whom the best known were Gandalf the Grey and Saruman the White. The other three were Radagast the Brown and two others known as the Blue Wizards, Alatar and Pallando, who travelled into the East of Middle-earth and never returned.
However, Voldemort, with his brutality and obsession with power, was undeniably the more dangerous one. While Grindelwald had a vision, Voldemort had a void he filled with terror and destruction, making him a deadly force no one dared to underestimate.
Radegast or Radogost is, according to medieval chroniclers, the god of the Polabian Slavs, whose temple was located in Rethra.
Obviously, radagast did not betray the valar in the same vein that Saruman did, which was very active betrayal of the mission. But he still failed to do ANYTHING AT ALL to stop Sauron. He does nothing. So he failed the valar.
Why was Sauron afraid of Aragorn potentially possessing the Ring? Gandalf explains it in the Return of the King (during the council after the battle of the Pelennor fields) that Sauron would never think somebody would want to destroy the One Ring.
But at the Council of Elrond, Gandalf very specifically says he fought all nine. He drew four of them off when he fled northward at dawn; "This helped, a little, for there were only five, not nine, when your camp was attacked."
But Radagast was weaker and his role overshadowed by Gandalf's achievements. Therefore it is difficult to conclude whether or not Radagast failed. But it is clear that Tolkien had doubts following his criticism of him in the Istari essay and Radagast certainly did not fall into evil.
The Wizard clad in brown was Radagast and the one clad in grey was Gandalf, seemingly the oldest and the least of the Order. The other two who travelled to the East and South were sometimes said to clad themselves in robes of sea-blue and were known as the Blue Wizards.
Tolkien's description of Gollum conforms to a Catholic – and Thomistic – account of envy, which is a “sadness of the soul”; and it is Gollum's unbearable sadness and his unquenchable desire for the one Ring that marks his character.
Gandalf is not permitted to use his full power during the 3rd Age (some exception apply). He has been sent to guide humans to the 4th age, the age of mortals. He can perform minor magic as needed, but he cannot "bust out."
Gandalf's true form was a spirit named Olorin. There's actually not a lot of info on Olorin in The Silmarillion, it is noted that he's one of only a few Maiar named in The Silmarillion, and that not much of him is known by the elves.
Unfinished Tales explains that Radagast, like the other Wizards, came from Valinor around the year 1000 of the Third Age of Middle-earth and was one of the angelic Maiar.
Why does Gandalf say he is Saruman when he comes back as 'Gandalf The White'? It was just a figure of speech, one might almost say; he was Saruman in the sense that he is now the head of the order or that he would be the good Saruman.
It's never confirmed how they met but Nagini and Grindlewald probably parted ways after he was defeated by Dumbledore in 1945. Nagini probably joined Voldemort early on and was probably one of his earliest followers and eventually found where he was hiding out in Albania.
Dumbledore ultimately overpowered Credence, but realised that he really was a Dumbledore - the son of Albus' brother Aberforth and thus Albus' nephew - after witnessing Credence's phoenix drop ashes on him.
He knew Voldemort could easily kill him, but he considered his imprisonment and death to be his penance for what he did, so he did not fear or resist Voldemort at all. In fact, he tried to mislead Voldemort by claiming that he'd never had the Elder Wand.
In Valinor, Gandalf, a Maia, was named Olórin, one of the people of the Vala Manwë, and the wisest of the Maiar.
Nori and the others are the reason Gandalf loves the Hobbits so much. He saw their purity of heart and through Nori he saw their potential to do great things.
On the show's second season finale, the Stranger is confirmed as a younger version of Gandalf, while the series creators J. D. Payne and Patrick McKay have indicated that the Dark Wizard is one of the other five, but extremely unlikely to be Saruman.