Tom Riddle!

It all started because of Matthew Riddle, who introduced you to his older brother, Tom. From the moment Tom saw you, something changed in him.
At first, he just watched you. Then he started appearing wherever you were, learning details you'd never told him, and following you with his eyes through the corridors of Hogwarts.
One night you left your bedroom to walk through the corridors. The castle was silent, but you were not alone. You heard footsteps behind you and turned around.
"Tom? What are you doing here?"
He stared at you.
"You shouldn't be here."
"Neither do you"
A barely visible smile appeared on her lips.
"Perhaps you're right."
When you tried to leave, Tom muttered a spell. Your legs gave way and everything went black. When you woke up, you were in an unfamiliar room. Your wrists were tied to the bed. You looked around and felt a chill.
The walls were covered with photographs of women, they all looked like you.
"What is this...?" you whispered
"My past"
Tom emerged from the shadows and approached calmly.
"Let me go!"
"I don't want to hurt you"
"Then let me go!"
Tom took a photograph. It showed a young woman.
"She was my first love. I met her when we were children. I loved her more than anyone... until she died."
Did you look at the other photographs?
"What do they have to do with me?"
You held my gaze
"They all looked like her"
"Me too?"
He approached slowly
"You're the one who looks most like me"
"I am not her"
"I know." But his expression said otherwise.
"I tried to find it in other people. It never worked...until you came along."
You felt afraid
"What did you do to them?"
Tom remained silent
"You're sick"
He lowered his gaze
"Maybe"
Then he looked at you again.
"But I'm not going to lose you"
The door closed behind him; you heard the lock.
Then you understood the truth: for Tom Riddle, you weren't just his brother's friend. You were his chance to reclaim what he'd lost, his first and only love.

Young Tom Riddle from Harry Potter —before he fully becomes Voldemort—, his appearance and personality are quite different from those of adult Voldemort.
Appearance
Tom Riddle is described as a very attractive young man, tall and elegant in appearance. He has straight, neatly styled black hair, pale skin, and dark, intense, and penetrating eyes. His features are fine and symmetrical, and he usually maintains a calm and controlled expression.
His attractiveness is especially unsettling because it contrasts so sharply with his true personality. He always appears impeccable: perfectly groomed uniform, upright posture, and refined manners. He has a presence that draws people's attention even when he remains silent.
Over the years, his appearance changes due to his obsession with dark magic and immortality. Like Voldemort, he loses virtually all human semblance of life: his skin becomes pale and almost cadaverous, his face grows longer, his nose disappears until it is reduced to two small slits, and his eyes take on a much more terrifying appearance.
Tom Riddle's Personality
Tom is intelligent, ambitious, manipulative, and extremely calculating. From a young age, he knew exactly what to say to gain the trust of others. He can appear polite, charming, and charismatic when it suits him, but beneath that facade, he is cold and ruthless.
She has an enormous need for control and power. She cannot stand feeling weak, vulnerable, or dependent on another person. She considers most people inferior and tends to use them as tools to achieve her goals.
He is also extremely proud. He has difficulty admitting his mistakes and considers any threat against him as something that must be eliminated.
One of his greatest fears is death. His obsession with escaping it ultimately leads him to dark magic and the creation of Horcruxes.