Bullies (1986)

"Heroes aren't born... They're cornered."

When the peaceful Morris family move to a small town and buy the town grocery store, they run afoul of the Cullen family. The Cullen's have been bullying the town's folk for years, and now they are harassing the Morris family every chance they get. Matt meanwhile meets and starts seeing a lot of Becky who also likes him. Unfortunately her last name is Cullen, and when the rest of the family finds out about their relationship, they decide to get even, and their harassment is elevated to vicious assault.