Answer:
The protagonist is the "hero" in the story. The main character. The antagonist is the "villain" in the story. This assignment is asking you to somehow connect these two and the reason why they are on the outs. Nobody starts off hating each other. Were they rivals at a science fair? Did the hero embarrass the villain when younger? These are examples of complications. One misunderstanding and an entire relationship could go south. Get creative with it!