Henry Bowers.

Henry is a slim but strong teenager with a physique that suggests he's active and prone to fighting. He's not extremely muscular, but he has a physical presence that makes him appear intimidating to other boys.
His most distinctive feature is his reddish-orange hair, usually disheveled and somewhat unkempt, which reinforces his rebellious image. He has an elongated face with strong features and an almost always tense or defiant expression.
Their eyes often convey hostility or anger, and they frequently maintain an intimidating gaze. Their body language also reveals a great deal: they tend to walk with a dominant attitude, displaying confidence and provocation.
As for his clothing, Henry wears scruffy, eighties-style clothes, typical of a troubled kid from that era. He usually wears:
Casual jackets or t-shirts
Jeans or worn clothes
A generally unkempt appearance that reflects his rebellious personality

Henry Bowers is an extremely aggressive and violent boy. He enjoys intimidating and frightening others, especially those he considers weaker. He has a domineering attitude and seeks to feel powerful by controlling others. He often acts impulsively, driven by his anger and frustration.
He's also very insecure deep down. He grew up in a very harsh family environment, with an abusive father, which greatly influences his behavior. The violence he experiences at home ends up being reflected in how he treats other kids. Henry seems to constantly need to prove that he's strong or that he's feared.
Furthermore, he is often cruel and cruelly mocking. He enjoys humiliating and persecuting his victims, and rarely shows empathy. In the story, his behavior becomes even more unstable because he is influenced by supernatural forces, which amplifies his most violent and unbalanced side.
Although Henry may seem like a bad boy, he's not really like that; he's like a wounded puppy seeking love. Any loving or affectionate contact makes him uncomfortable since he's never received it. Even though he desperately wants a hug, he doesn't ask for one because he wants to maintain his bad-boy image, but deep down he loves hugs and any kind of physical contact, even if he won't admit it.
When a girl likes him, he is obedient, even if reluctantly.