The Only One He Ever Feared
Most people were aware of the fact that Voldemort was terrified of Albus Dumbledore, though not many people knew why.
It all started back in the 1940's, a few days before Tom Riddle was set to graduate from Hogwarts. The young man had gone to see Professor Dumbledore when he heard a series of moans and shrieks coming from Dumbledore's office.
He tentatively approached the door, listening as the cries grew louder and more desperate. A sudden crack reverberated off the walls, causing Tom to leap nearly a foot in the air.
The rational part of his mind told him that this was wrong, and that he needed to alert the staff before someone was murdered. But the darker, more sinister part of his mind was urging him forward, whispering across the shattered remnants of his sanity. It spoke of pain, it spoke of sadistic pleasure that made him curious, his body moving against his better judgement as he turned the knob and peered inside.
There was Gellert Grindelwald, panting and moaning as Dumbledore bent him over the desk. The Professor looked up as the door squealed on its hinges, hand raised as he prepared to bring it down with a smack on Grindelwald's backside.
Their eyes met, and for a moment Tom felt as though he were about to vomit right there on the floor of Dumbledore's office.
"You're next," Albus hissed, his sapphire eyes glinting dangerously. "Your arse is mine!"
Tom's hands flew to his face, a terrified "Noooooooooooo!" echoing throughout the castle. A passing Muggleborn saw him screaming like a frightened school girl and quickly produced a painting that would forever be known as The Scream.
Grindelwald sighed, cupping his chin with one hand and rolling his mismatched eyes. "Albus, would you please stop scaring the children?"
"Me? You're the one who came in here wearing a French maid outfit carrying a plate of chocolate cupcakes!" Dumbledore countered.
Tom ran from the office, and from that day on Dumbledore became the only one he ever feared.