Alduin, known as the World Eater, was a very powerful dragon known for his rule over Skyrim during the Merethic Era. Though his exact origins are unknown the most accepted theory is that he was the first son of Akatosh, the Dragon God of Time.
During his reign over Skyrim, he and the other dragons were worshiped and revered as gods by the Dragon Cult, those that did not were forced into slavery. The humans began to rebel against his rule however when his lieutenant at the time, and younger brother, Paarthurnax, betrayed him by teaching the Thu'um to the humans. At the end of the war, Alduin was confronted by the Nord heroes, Hakon One-Eye, Felldir the Old and Gormlaith Golden-Hilt who used an Elder Scroll to banish him into the flow of time.
Alduin remerged in the 4th era and began to resurrect dead dragons to once again reign over Skyrim and end the world, after a confrontation with the Last Dragonborn on the Throat of the World, he retreated to Sovengarde where he started to devour the souls of the dead. The Dragonborn pursued him, however, and with the aid of the same heroes that defeated him eras ago, he was finally slain, and Nirn was free of his terror once again.
Battle vs. Rayquaza (by Richard Starkey)
No battle was written.
Rayquaza won this battle due to being faster, stronger, and having more powerful abilities.
Battle vs. Malefor (by Godzillavkk)
In a series of black volcanic mountains, Alduin lands on one of them, searching for the Dragonborn. 10 feet away, a massive purple dragon lands as well. Malefor stares at Alduin for a moment. "It seems you share similer goals to my own, but a mere mortal with similer powers could destroy you just as easily as you could? That's no trait of a dragon." Taunts the demonic dragon. "Such arrogance on your part. The Dovakin is a mere flea compared to me. I've heard of you as well, your prophisised enemy is a mere infant, your destined to be defeated by children. You dare call yourself dova? I think not." taunts Alduin.
Alduin is not amused by this. "You DARE mock me!? Spyro is a naive fly, and you will now suffer as he will suffer, PREPARE TO DIE!" Malefor leaps into the air and unleashes a blast of wind breath. Alduin digs his claws into the ground and holds against the wind for a while, but eventually gets blown back. Alduin recovers and shouts a series of dragon words, and meteors fall from the sky. One of them hits Malefor who falls to the ground. Aduin lets loose unrelending shout, but Malefor blocks with another blast of wind breath. Both attacks stop eachother. Malefor takes of again and breaths fear breath on Alduin. Alduin flys away briefly, but quickly recovers. Alduin lets loose a stream of fire at his enemy, but Malefor dodges.
Alduin flies streight for Malefor and the two dragons clash in midair. Both slash and bite evenly. Malefor eventually shakes Alduin off with some shadow breath. Alduin recovers and shoots a ball of fire at Malefor. The fire hits Malefor who falls down injured. As Alduin raises his claws, Malefor summons the last of his strength, and spits poison breath into Alduin's eyes.
Alduin shrieks in pain, as Malefor gets to his feet. Malefor grabs Alduin's throught, and bites down, until a loud snap is heard. Alduin falls down dead, while Malefor roars in victory.
Since Maelfor was suppost to represent Satan, and Alduin was not the greatest foe in Elder Scrolls lore(Trust me, there is a demon in the Elder Scrolls that's supposed to be Satan), Alduin was simply outclassed.
Battle vs. Flemeth (by JWarrior89)
The smell of cooked rabbit hung in the air as Morrigan stirred the stew which hung over the fire. As she lifted the spoon to have a taste, the door of the shack behind her opened, and Flemeth emerged.
"The stew is almost ready, mother." Morrigan said.
"Is it?" Flemeth asked, "From the smell it seems as if you have let it sit for too long."
"I know how to make stew, mother," Morrigan repled, annoyed, "I am not a child."
"Clearly not, for you speak to your own mother in such a respectful manner." Flemeth said, a slight smirk on her face. Morrigan opened her mouth to reply, but was cut off by what sounded like a distant roar.
"What was that?" she asked. Flemeth did not respond at first.
"It is nothing, child," she finally replied. She moved forward and sat down next to her daughter. Taking the spoon from her, she took a sip of the stew.
"As I suspected," she said, "you let it sit on the fire too long, foolish girl. The taste is ruined."
Morrigan opened her mouth again, but another roar silenced her words. This one sounded closer.
"There it is again!" She said. Flemeth said nothing, but instead got slowly to her feet, looking out over the lake.
"Leave, Morrigan." She said.
"What?" Morrigan asked, puzzled.
"I said leave. Now." Flemeth replied, more sternly.
"But..." Morrigan began.
"NOW!" Flemeth shouted at her. Morrigan quickly got up and ran for the edge of the forrest. Stopping for a moment, she looked back, looking worried. After a moment, she reluctantly turned back, transformed into a wolf, and ran into the trees, as the sound of flapping wings grew louder. Flemeth scanned the skies, looking for any sign of movement. Suddenly, with a rushing sound, something large flew above her, creating a gust of wind that blew over the pot of stew and exstinguished the fire.
"YOL!" A loud voice boomed overhead. Flemeth barely had time to react before the house behind her exploded in a massive fireball, throwing her to the ground. As she got to her feet, she turned to see a massive black dragon hovering over the remains of her house.
"Well, well, what have we here?" She said.
"Zu'u Alduin. Zok sahrot do naan ko Lein! Kel drey ni viik. Zu'u lost daal." The dragon said.
"So, you are the mighty Alduin?" Flemeth replied, smirking, "I expected you to be bigger."
"You are not Dovah, nor Dovahkiin, yet you understand our language..." Alduin said, slightly surprised. "Tell me, how is it that you expected my arrival?"
"A mutual acquaintance spoke to me of your... exploits." Flemeth said, "I suppose you can now add destroying an old woman's house to that list."
"This is nothing compared to what I have in store for you! Alduin said, "Daar Lein los dii! This world is mine!"
"Indeed?" Flemeth laughs, "I can see it now; the "mighty" Alduin soaring through the skies, scorching all that stands in your way! The world will shake before you!"
"Pahlok joorre! Hin kah fen kos bonaar!" Alduin roars, "Arrogant mortal! Your pride will be humbled! You are no match for a Dovah!"
"Perhaps I am a dragon." she said. As Alduin watched, Flemeth became enveloped in a bright orange glow. As the light faded, Alduin found himself no longer facing an old woman, but an enormous purple dragon, which opened its mouth wide and let out a ear-splitting roar. With a powerful flap of her wings, Flemeth flew upward, Alduin following close behind her.
"YOL TOOR SHUL!!!" Alduin yelled, a powerful stream of fire shooting out of his mouth towards Flemeth, who barely managed to avoid the blast. Turning around in mid air, she opened her mouth wide and unleashed her own stream of fire at Alduin, catching him full in the face. Alduin roared in pain, dropping a few feet before catching himself. Flemeth hovered in place and fired a few more bursts of flame.
"FUS RO DAH!!!" Alduin roared, sending a shockwave which blew Flemeth's bursts of flame aside and caused her to fly back a few feet. Before she could recover, Alduin flew forward, slamming into her. Flemeth roared with pain and anger as she flew further upward, Alduin in hot pursuit. For a few moments, the two dragons circled each other, firing streams of flame, but neither managing to land a hit. Suddenly, Flemeth turned and flew in the other direction. Alduin, roaring in fury, followed.
The lone guard stood at his post outside the city gates. His feet ached from standing there for so long, but he dared not leave, lest the Jarl punish him severely. He looked to his left, but there was nothing there. He glanced to his right. Again, he saw nothing.
"My cousin's off fighting dragons, and what do I get? Guard duty!" He complained to himself.
"Help!" A distant voice called out suddenly.
The guard's eyes snapped open as he turned his gaze towards the source of the noise. A farmer, his face covered in dirt and eyes wide in terror, was running towards him.
"Not him again..." the guard groaned. This farmer was always crying for help, wasting the guards' time with anything from stories of Werewolves stealing his cattle to conspiracy theories about people plotting to kill him. What was it this time?
"Let me guess," the guard asked the farmer in a mocking tone, "someone stole your sweetroll?"
"No, sir!" The farmer said, gasping for breath, "Dragons!"
"Excuse me?" The guard said, with a slight chuckle.
"Dragons, sir!" The farmer repeated, "Two of them! They flew over the mountains, heading right towards my farm! They'll be here any moment; you have to sound the alarm!"
"Look, son," the guard said, "I've had a long day, and I don't have time to be raising false alarms about dragons. Just go on home."
"But sir--!" the farmer began to protest, but a loud roar made him stop. Both he and the guard looked upward to see the two enormous dragons flying right towards them. The farmer cried out in terror and ran as the dragon in the back shot a blast of flame at the one in front, who flew upward to avoid it. The guardsman barely had time to cry out before he was incinerated.
Flemeth soared over the houses, glancing downward at all the townspeople running around in a panic. A roar told her Alduin was still in pursuit. It was clear to her that it was going to take some clever thinking to take him down. With a roar of her own, she flew toward the palace, situated at the top of a tall hill. Flapping her wings even harder, she managed to put considerable distance between herself and Alduin.
"Nivahriin joorre!" He roared, "Cowardly mortals! You feign bravery with clever words, but when faced with a true threat, you turn and flee! Devouring you will be doing this world a great service!" Ahead of him, he saw Flemeth fly around the right side of the palace. Intending to cut her off, he flew around the left side... but Flemeth had disappeared.
"Show yourself!" Alduin called out, flying upward. He began to shoot streams of fire in random directions angrily. Suddenly, a savage roar made him look upward, just in time to see Flemeth slam into him. Alduin was sent crashing to the ground below. Recovering quickly, he got up just as Flemeth landed a short distance from him. She let out a roar, which Alduin returned.
"YOL TOOR SHUL!!!" Alduin bellowed, shooting a stream of fire at Flemeth, who roared in pain as the flames scorched her scaly skin. She responded by spitting a fireball, which impacted with Alduin's face and exploded. Alduin growled and shook his head painfully, and Flemeth charged forward, slamming into Alduin and forcing him back. Alduin lashed out with his tail, striking Flemeth in the face. Shaking her head, Flemeth looked up just in time to see Alduin fly up into the sky. With a roar, she took off after him. Alduin had a considerable head start, however, and as she approached him, she heard him yell out something she couldn't make out. Suddenly, the skies darkened and became filled with menacing clouds. Without warning, flaming meteors began raining from the sky. Flemeth was forced to break off her pursuit of Alduin and avoid them. She flew out of the path of one, than another. Suddenly, with a rush, she felt something fly past her.
"FO KRAH DIIN!!!"
Flemeth roared with pain as she was hit with a jet of icy breath. She tried to fly away, but her movement felt sluggish; it was as if she was partially frozen. She barely had time to register this before a meteor slammed into her, knocking her out of the sky and sending her into a freefall. With a deafening thud, she slammed into the ground below. Flemeth could barely move as Alduin landed next to her.
"Nust wo ni qiilaan fen kos duaan..." he said. With that, he seized Flemeth's neck in his mighty jaws and tore out her throat. As Flemeth's blood spilled onto the ground, Alduin raised his head and roared in victory.
For what seemed like an eternity, there was nothing but blackness. Then, suddenly, there was a bright flash of orange light, and Flemeth felt life surge back into her. Opening her eyes, she saw that she was at the top of a mountain, overlooking the landscape below. Knowing what this meant, she turned around. Standing before her were two people. A young Dalish woman with short black hair, her face covered with tattoos, knelt before her.
"Andaran atish'an, Asha'bellanar." she said.
"Stand." Flemeth said, "The people bend their knee too quickly." She turned to the man standing next to the elf; he had brown hair and a short beard, and wore an iron helmet, studded armor, iron gauntlets and iron boots.
"I am glad to see there are still men alive who keep their word." Flemeth said, grinning.
"You saved my life," the man replied, "I didn't have a choice."
"We never do." Flemeth said. "I came across the dragon of which you spoke to me of. You were correct in saying he was quite powerful. Now that I know what he is capable of, however, I feel I am ready to show him my true power."
Flemeth turned her back to the man and gazed towards the horizon.
"We stand upon the precipice of change. The world fears the inevitable plummet into the abyss. Watch for that moment...and when it comes, do not hesitate to leap. It is only when you fall that you learn whether you can fly."
In a flash of orange light, Flemeth transformed once more into her dragon form. Spreading her wings wide, she took off, disappearing among the clouds.
Alduin had a far larger array of magical forms of environment-manipulation than flemeth - also, his physical strength would have easily matched, if not surpassed, Flemeth in her High Dragon form. It would have been a close fight in total, but The Voice would have been a far more useful tool than simply breathing fire, thus winning the fight.