Professor Albus Percival Wulfric Brian Dumbledore, Order of Merlin, First Class, Grand Sorc., D. Wiz., X.J.(sorc.), S. of Mag.Q., (July or August, 1881–30 June, 1997) was the Transfiguration Professor, and later Headmaster of Hogwarts School of Witchcraft and Wizardry. Professor Dumbledore also served as Supreme Mugwump of the International Confederation of Wizards (?–1995) and Chief Warlock of the Wizengamot (?–1995; 1996-1997). He was a half-blood wizard, the son of Percival and Kendra Dumbledore, and the elder brother of Aberforth and Ariana. His father died in Azkaban when Dumbledore was young, while his mother and sister were later accidentally killed. His early losses greatly affected him early on, even at his death, but in turn made him a better person. Albus Dumbledore was considered to be the most powerful wizard of his time. He was most famous for his defeat of Gellert Grindelwald, the discovery of the twelve uses of dragon's blood, and his work on alchemy with Nicolas Flamel.
It was through Dumbledore that resistance to the rise of Lord Voldemort was formed, as it was he who founded and led both the first and second Order of the Phoenix. Due to the fact that he had a keen mind and legendary power, Dumbledore became the only wizard that Voldemort ever feared. He was the wielder and the master of the Elder Wand from 1945 until 1997 and considered by many as the greatest Headmaster to ever grace Hogwarts. As he was about to die by a cursed ring, he planned his own death with Severus Snape. Though he was no longer alive at the time, it was through Dumbledore's machinations that Voldemort was ultimately defeated and peace restored to the wizarding world. He is the only Headmaster that was laid to rest at Hogwarts. Albus Dumbledore's portrait still remains at Hogwarts.
(taken from the Harry Potter wiki)
Battle vs. Gandalf the White (by Thornclaw Braveheart)
nside the Ministry of Magic's Hall of Prophecies, Albus Dumbledore and several members of his Order of the Phoenix (Sirius Black, Remus Lupin, Alastor Moody, and Kingsley Shacklebolt) search for any signs of Voldemort when they hear a thumping noise. Soon, the door at the far end of the hall is forced open as a white-haired old man in a white robe and bearing a white staff enters: Gandalf the White. In a magically-enhanced voice, he shouts, "I come for a Prophecy! The Prophecy of Olorin!" Dumbledore points his wand at the man and responds, "You come for what is not here! There is no and has ever been a Prophecy of Orlorin." Raising his staff, Gandalf casts a telekinetic spell, which causes one of the prophecy orbs to fall off it's shelf and smash. A ghostly figure emerges, speaking: "There shall come a time when the last ship of Mithlond...." Dumbledore waves his wand and the smoke emitting from the broken orb sinks to the ground. Gandalf walks forward. "I am Mithrandir, or Gandalf the White they call me in the North. Fight me if you must." Shacklebolt makes a humphing sound as Dumbledore turns to his fellow wizards. "Go to Grimmauld Place," he mutters, "And let me fight this person, whomever he shall be. I feel as if we have met before."
"We're not leaving you behind!" says Black.
"Go! One old man won't stop the Order!"
Moody turns to the wizards and nods. Almost at once, they Apparate out of the Hall. Dumbledore points his wand at Gandalf again and confronts him. "If I must fight you, I will."
"Are you a servant of the Black Eye?" Asks Gandalf. "Are you for him or against?"
"I know naught of this Black Eye," says Dumbledore, "and if I did, I would surely not be for him at all!"
Gandalf thinks through whether he should kill this person or not, when Dumbledore waves his wand and Gandalf flies through the air, Stunned. However, he recovers quickly and thrusts the air with his staff, sending Dumbledore flying. Standing up, Gandalf decides he doesn't need his sword right now and activates his light shaft, which blinds Dumbledore as he looks at it. Squinting, Dumbledore points randomly in the air and casts a Disarming Charm, but it simply bounces off one of the Hall's ceilings. Swinging his staff, Gandalf casts another spell, and Dumbledore is thrown to his side. The Headmaster of Hogwarts casts Expelliarmus, and it meets Gandalf's light shaft as the two spells connect in a fury of energy. Tendrils of magic strike out of the line connecting wand and staff, as suddenly Dumbledore swerves his wand to the side and the connected spells both crash into one of the racks of prophecy orbs. The entire rack shatters ad orbs continue to hit other racks, and in a domino effect the orbs continue to crash as Gandalf, aware of the danger, backs into the room he was just in. Dumbledore pursues, and when he enters, he realizes he is in the Time Room. Whipping his wand around, Dumbledore casts a Reductor Curse at a clock hanging on the wall, causing it to split into multiple fragments. Ducking under a glass container, Albus waits as Gandalf is struck by a piece of wood, but it has no lasting effect. Dumbledore appears from behind the case and casts a Stunning Spell on Mithrandir, who crumples to the ground, but then grabs his staff and casts his light shaft again. Dumbledore falls back, but then shakes the blinding light off and the two wizards exchange a flurry of spells once more until Dumbledore uses the Reductor Curse to smash a clock that falls right above Gandalf, but at the last moment the White Rider creates his bubble-like shield around him and the clock disintegrates on the shield. Using telekinesis to throw a Time Turner at Dumbledore, the Chief Mugwump blocks with his Shield Charm as Gandalf suddenly leaps over a wrecked glass box and draws Glamdring. Dumbledore realizes he left his weapon back in the Hall of Prophecies and casts a Summoning Charm, and an old hat flies into his hand. Dumbledore tucks away his wand and reaches into the hat, pulling out a spectacular sword. As Gandalf strikes, Dumbledore drops the hat and parries. The two exchange blows until Dumbledore is hit on the leg by Gandalf's staff, then cut on the upper arm by Glamdring. The Sword of Gryffindor cuts through part of Gandalf's robe, but the white wizard then kicks Dumbledore back and sees another door. He notices something strange in it, and so distracted is he that he almost misses deflecting Dumbledore's strike.
Noticing where Gandalf was looking, Dumbledore kicks him in the leg and leaps into the entrance, then walks forward into the Death Chamber. Gandalf stares at the floating rag in the middle of the chamber, with images of falling into an abyss, falling into a lake, chasing a fire demon up an endless staircase, and finally casting down the demon from a mountain peak and passing away from wounds flash through his mind. Tears float down his face, but then he casts telekinesis, and Dumbledore is thrown back some more. Bleeding from this injury to his chin, Albus picks up Gryffindor's Sword and tucks it in his belt. He then draws his wand and fire emite from it. Gandalf climbs up to the veil in the center of the Death Chamber and is about to stick his hand through the archway when an unseen force makes him stop. He turns to Dumbledore, and suddenly the two are encirclced by fire. Dumbledore ends his spell as the inferno engulfs the chamber, and he turns to Gandalf. "You should never have come. You would have lived yet a little longer if you remained wherever you came from."
Lifting up both staff and sword to create his Shield of Istari, Gandalf replies, "If you are so certain of my demise, then prove it!" Raising his wand, Albus Dumbledore casts a Reductor Curse, which weakens Gandalf's Shield but fails to penetrate. Grunting from the strong blow, Gandalf holds his shield firm as Dumbledore creates his fire lasso and repeatedly slashes at the shield until he sees the bubble of power flicker, then disappear. Taking advantage, Dumbledore runs forward, but Gandalf lifts his weapons again and brings them together, smashing the staff on the ground as it cracks. The floor cracks as well, and suddenly the entire room crumbles into itself as Dumbledore hurriedly Apparates out of there. However, Gandalf abandons his broken staff and, right before the Headmaster leaves, grabs ahold of him and they exit together, all the while struggling for control of Dumbledore's wand.
Somehow Gandalf gets Glamdring stuck somewhere and uses both hands to wrestle the Elder Wand out of Dumbledore's grasp, then suddenly thinks of somewhere in Middle-earth. Abruptly, the two wizards end the Apparation spell as they end up standing right at the edge of the broken bridge in Khazad-dum. Dumbledore, shocked at his surroundings, fails to see that Glamdring was impaled in his stomach. Gasping in the pain, he steps back, and Gandalf grabs the sword and pulls it free as Albus Dumbledore falls into the abyss below. Gandalf sheathes his sword and looks at the Elder Wand. "Hmm...not bad..." Walking away, he waves the wand and Disapparates.
WINNER: Gandalf the White!
Although close when it comes to magic, Gandalf's more superior close range weapons and brute force of his spells prove stronger than Dumbledore's mostly non-lethal spells. So when it comes to master wizards, once again NOTHIN BEATS THE LORD OF THE RINGS!
Battles here were deemed to be unfair or otherwise not in accordance with wiki standards, and have been removed from the statuses of the warriors and displayed below.
Battle vs. Master Chief (by Lachlan Blake)
Dumbledore stood in his office, extracting memories and depositing them in small bottles, he placed one down on his desk and sat down. Suddenly, his desk began to shake, he stood and looked at the bottle moving on the desk and then stepped back. A blinding light filled the office, and John appeared in the middle of the room.
"CHIEF? are you ok? There must have been a malfunction in the Pillar of Autumn's slipspace transition drive... careful chief, I'm not picking up any UNSC transmitions." Said Cortana, in mastershief's helmet.
"And who are you, statue?" said dumbeldore, cautiously.
Masterchief pulled out his pistol, but dumbeldore was quicker, and let out a spell that knoked John into the wall. John recovered and shot his pistol a few times, missing Dumbledore, who teleported to the other side of the room.
"Oh, so you are using muggle weapons, are you a ro-bot?" Said dumbledore teleporting and casting a spell which bounced of chief's sheilds. John took out his SMG in his left hand, and fired full-auto across the room, he anticipated one of dumbledore's movements and hit him in his arm. Dumbledore responded by making his table fly at John, pinning him to the wall. Masterchief slipped beneath the desk and ran at dumbledore, tackling him to the ground, discarding his pistol and pulling out his assult rifle he went for a point blank shot, but dumbledore shot a shockwave at John, making him hit the roof.
"John look out!" said cortana.
Several killing curses flew at John, one taking down his sheilds, and two barely missing him. Dumbledore then began casting a lengthy spell, the light dimmed and electricity flew around as Dumbledore made a ball of electricity, blasting it at john, who was hit directly, paralising him and knocking him into the opposite wall, John struggled to move as dumbledore advanced, preparing a powerful spell that would surley kill this armoured opponent.
With a lighting fast movement the chief recovered, and shot a round at dumbledore, hitting his chest. The wizard fell to his knees as the chief shot him with his battle rifle.
The chief walked silently out of the room, with Cortana telling him to find some kind of teleportation device.
WINNER: MASTER CHIEF.
Master Chief was victorious because he wielded far more advanced weaponry and defenses which allowed him protection against Dumbledore's spells, and he had superhuman augmentations in combination with his training, giving him greater battlefield skill than the Headmaster.