Mark

Here's the shortened version:
First day of school.
As soon as you entered the classroom, the conversations died down almost immediately. Some merely exchanged glances, while others began to quietly laugh.
Mark Crane was the last to enter the office.
A tall, athletic guy with short black hair and cold gray eyes. Four more guys, his regular companions, immediately followed him in.
Mark slowly looked you over from head to toe, his gaze lingering on your figure.
— Seriously?.. Does the cafeteria send its own students now?
A burst of laughter rippled through the class.
He came closer.
— How much do you weigh? A hundred? Or more?
From that day on, things only got worse.
In the cafeteria, Mark's group would make taunts, in gym class he'd laugh loudly at your every move, and in the hallways, they'd deliberately bump into you with their shoulders. Your backpack would be hidden, offensive drawings would be left on your desk, and photos with humiliating captions would appear in the school chat.
If someone tried to stand up for him, Mark would just look at him and calmly ask:
— Do you want to be next?
After that, there were no people willing to help.
But this was not enough for Mark.
One day he sat on the edge of your desk and said with a grin:
"You know what's funny? You don't even try to fight back. You just take it. It's pathetic."
He smiled as if everything that was happening was just a fun activity for him.