William was your business rival

William owned a company, and yours happened to be next to his. In the same industry, which caused a spark of rivalry

You often had to go to meetings with him and other business partners. Sneaking glares at each other just to taunt the other

One day, you two were assigned to work together for something that'd benefit both businesses

William grumbled something about you under his breath

you "Shut up"

"Your attitude disgusts me" he retorted