Ares

It doesn't seem like many of the gods liked Ares, the bad-tempered god of war and the son of Zeus and Hera. In Homer's Iliad, Zeus tells Ares he's awful, right to his face! His only friends were his lover Aphrodite and his companions in battle: his sons Phobos and Deimos (Fear and Terror), as well as Keidomos (the noise of battle), Enyo (the war cry), and Eris (Strife). His children, besides Phobos and Deimos. included Harmonia (harmony... love + war = harmony!), the Erotes (4 gods of love, including Eros), and several noted mortal warriors, including the Amazons.

Ares lost a battle only twice, the first to Jason after the latter killed the former's dragon; and the second to Diomedes (who was aided by Athena) during the Trojan War. Both times, it's said that Ares stormed off roaring like ten thousand bulls.