Antagonism (noun)

1. Active hostility or opposition towards someone or something.
2. A state of opposition or hostility between people or groups.

Origin:

Late 16th century (in the sense "struggle for superiority"): from french antagonisme or late latin antagonismus, from greek antagōnismos "opposition", from antagōnizesthai "to struggle against", from ant- "against" + agōn "contest".

Examples:

1. There was a strong antagonism between the two sides.
2. The antagonism between the two countries has been escalating.
3. He felt a deep antagonism towards his brother.
4. The antagonism between the two sides was clearly visible.
5. The antagonism between the two groups led to a lot of tension.