Humiliated school boy
I like the idea of a humiliated schoolboy, particularly by the school bully. Ny two ideas were:
A teacher sending the boy to detention and being nice at first, but teasing him with her body. Then making him jerk off "like a good little boy", being nice but very condescending. And then getting meaner as it goes on, telling him he is not good enough to fuck any girls, and that if he was a big boy like the school bully he would get to fuck her like the bully does.
A kind of loser kid who manages to get a very sweet pretty girlfriend who always sticks up for him and hates the school bully. However the bully manages to seduce the girlfriend and she loves his big dick. In the end the girlfriend ties her boyfriend to a chair and fucks the school bully in front of him.