Few armies could actually stand against the forces of Mordor, mostly because of its huge and seemingly endless size. Yet, as seen in the opening of The Lord of the Rings: The Fellowship of the Ring, The Last Alliance between men and elves were able to push back Sauron's army and were winning before he entered the battle. Knowing the fate of Middle-earth's forces against Sauron, it's interesting to look at what other fantasy armies could take him on. For example, could Daenerys Targaryen's army from Game of Thrones take on the might of Sauron?
Daenerys' Army's Strength and Weaknesses
What Daenerys' army lacks in size, it makes up for in skill. Still, the size of her army in Game of Thrones Season 8 is nothing to scoff at. With around 100,000 Dothraki and 8,000 Unsullied, she could already take on Westeros. Yet, she gains allies along the way, including thousands of northerners and naval forces from House Tyrell. And, of course, Daenerys has her three dragons to pierce through armies.
The soldiers' skills would be what tip the battle against Sauron in her favor. The Dothraki are savage fighters who spend their life lusting for conflict. Paired with their skill on horses, they could cut through orc and Uruk-hai, much like in the battle of Minas Tirith. The Unsullied -- although short in numbers -- are perhaps the most skilled of all. With their sole purpose in life being to train and fight, they could easily take on orcs who have had significantly less disciplined training. After seeing how Daenerys' three dragons destroyed most of King's Landing, they could easily unleash huge devastation on the battlefield.
However, looking at the armys' weaknesses, it seems likely that they wouldn't be able to hold off the sheer number of Sauron's orcs. As seen when the White Walkers attacked Winterfell, Daenerys' soldiers could not withstand overwhelming waves of enemies charging at them. Also, the Dothraki aren't known for their disciplined and well-formed battle-tactics, so running full force into Sauron's army may be their demise. When it comes to Daenerys' dragons, two were killed by well-placed artillery before they even reached the main battle for Westeros. Therefore, it's likely Sauron would have appropriate weapons made for dealing with them.
Sauron's Army's Strength and Weaknesses
If the One Ring wasn't cast into the fires of Mount Doom, then it's likely that Sauron's forces would've taken control of Middle-earth. Although there aren't specific numbers, the orcs from Mordor look to be well above 100,000, with a seemingly endless amount pouring out. Yet, orcs aren't the only race faction who follow the Dark Lord.
There's no doubt that Sauron's army would overwhelm Daenerys'. Not only is the army huge, but it has a much wider variety of fighters. Easterlings, Trolls, Wargs, Uruk-Hai, goblins and many clans of men all follow him, and each with their own specialties. Then, there's the more magical side of his army, with the Nazgûl mounted upon their fellbeasts able to attack and strike terror, much like Daenerys' dragons. And, of course, Sauron himself, who in physical form could not be defeated by anyone in Daenerys' army.
As for Sauron's weaknesses, it's known that orc aren't the best of fighters, and most who follow him tend to be weak-minded. While the Haradrim rode massive oliphant into battle, it seems little of Sauron's army has cavalry, which is often seen cutting through his armies like butter. And there's no forgetting the One Ring itself. Sauron's greatest power in the fight would also be his greatest weakness if discovered, as the battle would be over if cut from his hand or destroyed.
Winner: Sauron
No matter the skill, the overwhelming size of Sauron's army would continuously hit against Daenerys' until there was nothing left. Although her army would put up a good fight, their defenses aren't their strong suit, and the dragons could be dead before making a huge impact. But there's always a chance. If Daenerys made the One Ring her prime target, it could lead to Sauron's demise once again.