Adjectve: Agonistic (ag-uh-NISS-tik)
2. Striving for effect: strained.
3. Of, relating to, or being aggressive or defensive social interaction (as fighting, fleeing, or submitting) between individuals usually of the same species.
Sample sentence: No matter how much we try to get along, there is always an agonistic moment between my sister and I when we get together for a visit.