At 14 years old, 6'1" (with thick curly hair adding another couple inches) and 260 pounds I easily had 100-125 pounds and several inches on most kids. Pus I'm built like a fullback, sure I was chubby but I was also pretty damn strong with shoulders wider than most grown men and was being eyed by the high school football and wrestling teams as early as 7th grade.
I've never really gotten into anything more than a playground scuffle but I do remember one instance of landing a terrifying punch. It was the day after a kid sucker punched me in the stomach which left me humiliated and crying in the street (hit me square in the solar plexus-his dad was a doctor and i believe he'd been coaching him on anatomy in retalliation because I unknowingly sold them a broken lawnmower). In math class the next day I landed a single, thunderous blow into the kids shoulder. The thud was so loud that the room came to a hush and I thought I'd killed the poor kid. He was stunned for a minute but brushed it off. I could tell that I caused him physical pain and watched his arm droop for a short time. I felt terribly guilty about that for quite awhile. We eventually reconciled and other than the time I accidentally stepped on his face (ouch) and possibly broke his nose (yikes) when they tried the old "one person kneel behind me and another push me over trick". If you're wondering- you can't really make a 260 pound kid fall over but you can make him lose his footing. In such a situation it isn't wise to be kneeling down with one's face in the vacinity of the giant's lumbering foot.
There were times that I wanted to fight but two things would stop me. First, my conscience. I was never comfortable with the idea of hurting someone even if they had hurt me. The second reason is that the school would charge a $200 fine to any student caught fighting whether in self defense or not. Being poor and not wanting to cause my (single) mother any hardships I always kept my hands in my pockets. Now that I'm 32 years old I believe this fine was a lie.
There was one instance that I'm especially proud of. I was in 12th grade and my growing had stopped so I wasn't the biggest kid anymore but still quite large. There was a special needs student who I knew a little but not much. He had some physical and mental problems but also seemed to occasionally be standoffish. Nonetheless I would say hi to him and did carry his books or help him to class if he got lost again. One day he was trying to open a soda bottle and accidentally dropped it. He picked it up and the jarring made the soda burst out all over the hall and other students when he opened it. Everyone was cool with it except this one little **** head. The little **** head pushed the disabled boy and well, I hit the freaking ceiling. The shithead didn't know I was watching the entire thing and I ran over to stand between them. I stared this kid down. I will never forget look in his eyes that was a mix of utter shock and "oh my god I'm going to die". Man, if I could have had a camera. I didn't have to lay a finger on him, my point was well-received.
You don't have to fight to win.