He literally is not a man.

The sense is that Gandalf seemed too powerful and the director decided to humble him a bit to add tension.

Have to watch the Bakshi version for that! 

And it was cool as fuck scene

I wouldn't say that. I'd say he did a great job adapting text to a visual medium. In the text just having the sword light on fire in preparation works. When you see it played out, everyone is going to ask why he didn't take a swing before leaving.

THÖŪ FÖÖL NNNYA-AH-AH-AHHH

This is exactly what the previous comment is saying. Jackson changed stuff for the movies to cater to mainstream movie audience expectations, at the cost of the worldbuilding and lore.

Maybe having a guy that's totally invulnerable to the most powerful bad guys is actually not great world building in the first place.

He's not at all invulnerable, in the book they were about to throw down and the Witch King was pretty confident about his chances. Also Gandalf literally gets killed by the Balrog.

HERESY!!!! /s

Yes pre-super Saiyan Gandalf is weaker.

Dude really just "Go home, boy" the ghost.

The Witch King was still gonna go him.

Both happened before Gandalf got cleaned up though.

Meaning both he and the Balrog lose a lot of their power in physical form in the first place but yeah

Balrog who is also a Maia* Maiar is plural

The Witch-King can fight a wizard for the same reason elves can fight and kill the greatest dragons and balrogs themselves. Binding creatures of spirit into physical form both weakens them and makes them vulnerable to other creatures built of both natures. That the Witch King is the equal of a balrog/Maia is not a stretch... Gandalf bring afraid of him even if he is a threat is the stretch.

Especially with prep time.

That's the thing though, it's not invulnerability, it's, for lack of a better term, will realized as magic. In Moria, > "...Gandalf **stood firm**. '**You cannot pass**,' he said. The orcs **stood still**, and a **dead silence fell**. 'I am a servant of the **Secret Fire**, wielder of the **flame of Anor**. You cannot pass. The **dark fire** will not avail you, **flame of Udûn**. **Go back to the Shadow! You cannot pass**.' This is an invocation - You cannot pass, I am a Maia of Eru, wielder of Narya, Morgoth is gone, Balrog, *You cannot pass* - and he does, indeed, not pass. At Gondor, the actual fight starts earlier: > For yet another weapon, [..] the Lord of the Dark Tower had: dread and despair. The Nazgul came again, [..] More unbearable they became, not less, at each new cry. At length even the stout-hearted would fling themselves to the ground as the hidden menace passed over them, [..] and they thought no more of war; but only of hiding and of crawling, and of death. And so, > So it was that Gandalf took command [..] Wherever he came men’s hearts would lift again, and the winged shadows pass from memory. [..] And yet – when they had gone, the shadows closed on men again And, finally, >"There waiting, **silent and still** in the space before the Gate, sat Gandalf [..] '**You cannot enter here**,’ said Gandalf, and **the huge shadow halted**. ‘Go back to the abyss prepared for you! **Go back**! Fall into the nothingness that awaits you and your Master. Go!’" The Witch-King responds: "‘Old fool! This is my hour. **Do you not know Death when you see it?** Die now and curse in vain!’" and lifts his sword to strike, and then: "Gandalf **did not move**. [..] a cock crowed. Shrill and clear he crowed, **recking nothing of wizardry or war** [..] And as if in answer there came from far away another note. Horns, horns, horns. [..] The darkness was breaking too soon, **before the date that his Master had set for it**: [..] he left the Gate and vanished." The night assault was driven by the ringwraith terror. Gandalf doesn't confront the Witch King physically, he denies his terror, and denies him entry, and when he, unwisely, forces a confrontation, his whole spell folds like a cheap suit.

Dragons weren't spiritual creatures bound into physical form. They were something Morgoth basically selectively bred.