Powerful creatures of ME

[Jonathan]

There have been many mighty creatures roaming the lands of Middle-Earth. I want to discuss which of the creatures that is the most powerful. I have selected three candidates from The Hobbit and Lord of the Rings to the title "the most powerful creature of Middle-Earth". I have left out creatures mentioned in other books of Tolkien, like Ungoliant. Let's also skip people like the wizards, the valar, the elves, the Uruk-hai and Sauron.
My candidates are:

The dragon Smaug, who we could read about in The Hobbit. Smaug lived in the Lonely Mountain, where he guarded a huge dwarven treasure. The mighty dragon described himself like this:
"My armour is like tenfold shields, my teeth are swords, my claws spears, the shock of my tail a thunderbolt, my wings a hurricane, and my breath death!"

But in the end of The Hobbit, the dragon was slain by the bowman Bard of Laketown. If Smaug was killed by a human, maybe he wasn't that great after all?

The spider-shaped Shelob, who dwelt in the mountains on the western borders of Mordor. In LotR, we could read of how she fed on orcs, and that Sauron deliberately sent orcs to her. The Shelob could have been a powerful servant of Sauron, but I believe that she to powerful to be controlled. To have Sauron feeding her says much of her power

But if the Shelob was so powerful, how could a little hobbit like Sam wound her as much as he did in The Two Towers?

The Balrog of Moria, known as Durin's bane. The creature could shroud himself in darkness and engulfed himself in flames. In The Fellowship of the Ring, the Company of the Ring travelled through Moria and ran into Durin's bane. He seemed to equal Gandalf's powers, at that says much of how mighty the Balrog was. The two Maiar clashed and fell into the deepest caverns beneath Moria.

After pursuing the Balrog for a week and fighting a though battle for two days, the Balrog was defeated. Not many creatures in Middle-Earth could prove to be such a challenge for Gandalf. The wizard was even "killed", stressing the incredible power of the Balrog.

Then there are very powerful creatures like the ents (who singlehandedly destroyed Isengard), the Nazgûl, Gwaihir and the Eagles, Beorn, Tom Bombadil and maybe the Oliphaunts.

Now, who is the most powerful? Some would claim that no one is as powerful as Smaug, since "he is the biggest of them all".
Others would say that the Balrog could beat Smaug any day.
Perhaps the Shelob has some fans saying that she is the most powerful.
Personally, I would say the Balrog is the strongest. What do the other 'mooters think?