It might also be worth mentioning that among the many books, commentaries and articles I've read about LOTR and M-E it was very convincingly pointed out that Wizards, while having great power, were particularly great against other magical individuals of great power (like the Balrog), and not necessarily so useful in a common fight with slings and stones, whereupon wit and wisdom served better. The capacity to wreak great ruin among his numerous foes was limited to his more "earthbound" skills, such as with gunpowder and fiery pine cones (oh dread!).
This may possibly have had something to do with the limits of his proscribed duties, but even the great among the ancient elves, for example, could only slay people one sword swipe or arrow at a time, even though many Great Lords of Elven kind waxed extremely powerful during their visit to Valinor, overshadowing their own kindred who remained behind. Some appeared to approach Even lesser Maia-like potency and ability. Gandalf was surely as great as any Elf Lord.
The great Girdle of Melian is an example of the kind of power a "good" Maia could wield, and was defensive rather than offensive and destructive, so it's doubtful whether Gandalf, even as Olorin, would, could, or might be inclined to cause his enemies to vanish in a great cloud of smoking ruin, even if he had great need to do so. The "Powers" of Middle Earth appeared to be more that of empowering and dominating, or influencing and convincing, great masses of others to do all of the slaying for them. Otherwise, the "good guys" so respected life and creation that it's probably not even in their realm of thought to overly consider the arts of mass destruction.