Serving as a protector of Earth for decades and Asgard for millennia, Thor has been in more battles than almost any superhero in Marvel.
He has waged war against entire armies single-handedly, eradicated monsters in all of The Nine Realms, and has taken down more Dark Elves, Fire Trolls, and soul-eaters than he can remember. He's so freakin' awesome, he managed to kick butt when he was turned into a frog, for crying out loud! Most heroes may struggle to thwart a cosmic entity or an intergalactic empire - but for Thor, it is often mere sport.
But every once in a while, the golden-haired superhero will face a foe that cannot be defeated with a single swing from his enchanted hammer. He may be the god of thunder and occasional All-father of Asgard but the Norse champion has come across enemies that were able to hold their own against the founding Avenger.
Even when he is armed with his entrusted Mjolnir and assisted by the forces of Earth and Asgard, there are some villains that The Mighty Thor struggled against. Whether it's a slayer of gods or a consumer of realities, these are the battles that Thor will remember until his dying day.
10. Apocalypse - Uncanny Avengers #6 (2013)
En Sabuh Nur was born a mutant in Ancient Egypt in 3000 BC. After fusing with Celestial technology, he became the most powerful mutant on Earth and dubbed himself Apocalypse. Because he's attempted to conquer the world for millennia, it seemed inevitable that he and Thor would cross paths at some point.
In 1013 AD, Apocalypse made his way to Scandinavia after learning its people posed a threat to his schemes. Thor happened to be nearby and, despite being heavily inebriated, challenged the demonic demagogue, assuming he was a mindless brute. Because this encounter took place before Thor was armed with Mjolnir, Apocalypse wiped the floor with the Viking god. When Thor realised his axe, Jarnbjorn, couldn't pierce his enemy's Celestial hide, he fled back to Asgard.
After seeking consultation, the thunder god learned he could place an enchantment on his weapon using his own blood to make it cut through anything. After doing so, he tracked down the Celestial-powered mutant and demanded a rematch. This time, Thor's axe cut through his rival's chest with ease. Left with no choice, Apocalypse reluctantly retreated.