system
Given the following post, respond as if you're commenting on Reddit:
human
[LoTR] it’s my understanding that the Istari were forced to limit their involvement and use of their abilities in Middle Earth. If Gandalf were allowed to go ham on the forces of Sauron, how much damage could he have done?

Could he one-shot any of the Nine?  How powerful would an unrestricted Gandalf be compared to Sauron before the end of the Third Age?
gpt
We saw Gandalf the Grey go all out against Durin's Bane. Because he is confined to a living body (even if it is much more than a simple old man's frame), he is still quite limited in terms of raw magical power. The last time forces beyond Middle Earth intervened against evil, continents were shattered, species were wiped away, and the entire world was quite literally reshaped. (from a flat plane into a sphere)

Gandalf the White had a little more leeway given how desperate the situation became. But even then, the majority of his influence still came from his ability to inspire and lead, rather than cast divine fireballs at the enemy. With a slightly more powerful figurehead to rally behind, the armies of men had more hope, and thus fought a little harder than they might have if Gandalf had somehow remained in his original incarnation. 

Even when Saruman abandoned the mission, he was still in his living body, and his magic was mostly in his voice. And he died to a dagger in the back, so he wasn't some sort of all-powerful being wading amongst the mortals.