rancorous (adjective)

1. The rancorous rivalry between the two main characters in the anime series caused constant conflict and tension.

2. The rancorous disputes between the British and American colonists eventually led to the American Revolution.

3. The rancorous feud between the Montagues and Capulets in Shakespeare's Romeo and Juliet resulted in multiple tragic deaths.

4. The rancorous criticism among fashion designers about each other's creations often leads to heated debates and arguments during fashion shows.