Dumbledore's greatest fear was finding out who actually cast the spell that killed his sister Ariana. It was either Dumbledore himself, his brother Aberforth, or Grindlewald. I believe it was Grinldelwald because he fled the country after her death and Dumbledore never saw him again until their legendary duel in 1945. Dumbledore's reason for delaying his meeting with Grindelwald was because he was afraid he would find out the truth.
The ministry of magic has an unfounded fear that Dumbledore wants to take over the ministry.
Albus Dumbledore's brother is Aberforth Dumbledore.
Dumbledore's full name is Albus Percival Wulfric Brian Dumbledore.
Gellert Grindlewald, but mostly because he loved him and knew he would be rejected. Grindlewald also made him feel guilty about his sister's death.
Dumbledore, obviously.
He always thought he controlled Severus Snape and had no reason to fear him. The only person Voldemort ever feared was Albus Dumbledore.
No, Dumbledore is too old for her.
Dumbledore's young sister.
It is spelled Dumbledore.
No. Dumbledore is a fictional character.
Voldemort was afraid of Dumbledore and never willingly sought a fight with him. The only time we know of that the two dueled was during the Battle of the Department of Mysteries at the end of Harry's fifth year. Voldemort tries very hard on that occasion to kill Dumbledore, but he is unsuccessful and forced to flee. Voldemort who fears death above all else, likely did not seek to kill Dumbledore himself for fear the other would beat him through superior skill.
Dumbledore's full name is Albus Percival Wulfric Brian Dumbledore, giving him three middle names.