Diomedes
Diomedes might possibly be the most insane, over-the-top asskicker from the Trojan War. Sure, Achilles, Ajax, Hector, and Odysseus get most of the ink when you're talking about sack-kicking hardasses from the epic ten-year Ionian bloodbath, but the significantly less talked-about King of Argos performed towering acts of bone-crunching awesomeness on par with the greatest deeds of any of those mighty warriors. Plus he went into battle with a shield that also doubled as a flamethrower, and this is a point that I can't possibly emphasize enough.
Even before the glory days assaulting the golden walls of Illium with a giant spear drenched in the blood of torn-to-shit Trojans, Diomedes kicked ass. A favorite of the mega-hardcore warrior-goddess Athena (and the only mortal man to have ever seen her in her full divine form), Diomedes was blessed with wisdom, strength, and cunning well beyond his years, and he usually employed this particular skillset in the business of wrecking the asses of all of his enemies. The first chumps to feel this wrath were the citizens of Thebes. Diomedes' father was a member of the Seven Against Thebes – a legendary group of seven warriors who led an army against the heavily-defended city. The Seven were defeated out of hand, their leader was slain and left to die in a field somewhere, and Diomedes' father returned home reeking of failure and defeat and cabbage. As a teenager, Diomedes sought to correct that bullshit right quick. He joined the Epigoni, which was comprised of the seven sons of the Seven Against Thebes, attacked the city once again, destroyed the defending forces, and pulled down the walls of the city.
Incidentally, this much-celebrated battle was more military experience than many of the Greek generals had when they left for Troy, and though Diomedes was the youngest military commander to lead warriors across the Aegean he was also among the wisest, the strongest, and the most accomplished. It also bears mentioning that Diomedes was a one-time suitor of the oft-lusted-after Helen, and that when he departed the shores of Greece he brought 80 ships with him, which was the second largest invasion force behind only Agamemnon - the overall commander of all Greek forces in Troy.
Once the war was in full swing, Diomedes only continued to assert his bronzed balls and subtle knack for cleaving people apart at the neck. For starters, this guy was huge and completely crap-your-pants scary. He charged into battle wearing impenetrable armor crafted by the forge-god Hephaestus, which was emblazoned with images of some badass pointy-tusked wild boars. If it's not enough that he carried a wide variety of weaponry and wore sword-proof armor, he also had a shield and a helmet that were enchanted by Athena to blast out fireballs like some kind of goddamned flamethrower.
Igniting enemy warriors with a searing-hot jet of flaming liquid is great, but Diomedes was more than capable of busting people apart the old-fashioned way as well. According to Homer, this head-crushing behemoth was second only to Achilles in terms of fighting ability and blood-raging fury, a fact supported by the ridiculous body count he piles up throughout the Iliad. In the brutal ten-year showdown, Diomedes kills a couple Princes of Troy, some Amazons, and whatever the hell else he feels is pissing him off at the time. The Iliad lists nearly thirty names of warriors killed by Diomedes, along with several other excerpts mentioning him "freaking the fuck out and murdering a shitload of people with his dick", so we can assume that this guy was at least somewhat competent in the field of making people his bitches.
But the wanton slaughter of enemy warriors is just the beginning of Diomedes' awesomeness. At one point during the war, he actually came face-to-face with another epic hero – the mighty Aeneas. Diomedes took one look at this warlike member of the Trojan royal family, brained him in the face with a huge-ass rock, and then rand in to slice the dude's head off and destroy the Roman Empire before it was sperm. The goddess Aphrodite, seeing Aeneas in trouble, swooped down from Olympus, snatched the badly-wounded Trojan hero up into her arms, and ordered Diomedes to stop.
Diomedes told her to get fucked. With Athena guiding his sword arm, Diomedes charged forward, striking Aphrodite in the arm and causing her to cry out in pain. She dropped Aeneas and fled back to Olympus while he yelled taunts at her. If beating up fertility goddesses isn't hardcore enough for you, when Apollo rushed in to carry Aeneas away, Diomedes also attacked him three times, only to be repelled by blinding flashes of light each time. This guy just didn't give a shit – he would take on any one, any place, any time, regardless of their potential status as being immortal, or, you know, whether or not they were his gods.
Never was this more intensely awesome than when Diomedes, the mortal son of some moderately-important guy, went straight-up against Ares, the Greek God of War, in mortal combat. That's right, this guy was so utterly fearless that he fought the deity responsible for warlike bloodshed, and the being whose sole job is to decide who wins battles. Oh yeah, and as he was charging in to do battle with Ares Himself, Athena warped down into Diomedes' chariot, guided his arm, and the Greek hero threw a fucking spear that wounded the god of war, sending him running back home crying like a punk bitch. The only analogy I can really make here is that this is like playing a game of D&D, deciding to have your character attack the Dungeon Master, and winning.
It's hard to top something like out-dueling the god of war, but it does bear mentioning that Diomedes also bests many of the Trojan War's greatest heroes in tests of strength and skill. He defeats Hector in a duel by cracking him in the skull with a javelin. He beats up Ajax in a full-contact sparring match, which is actually stopped by the Greek generals when they see Diomedes' fury and fear for Ajax's life. He outruns Odysseus in a footrace, and wins a badass Ben-Hur-style chariot race against many other Greek heroes.
Diomedes also played an understated role as a badass Greek special forces commando during the war. He and Odysseus went on a couple of espionage missions that had far-reaching implications for the allied victory against Troy, including one time when they broke into the city and stole the Palladium (the most holy and revered artifact the Trojans had), and another time when they assassinated the King of Thrace in his palace and stole off with his horses. The most famous of these covert operations, however, was the famous Trojan Horse mission. Diomedes was one of the warriors inside the belly of the wooden horse that was led into the city, and he was one of the motherfuckers that set fire to Troy, destroyed the city, and ended the war in a giant cataclysm of bloody explosions.
After the war, Diomedes returned home to find that his wife was no longer interested in having him around (the myths attribute this change of heart to the work of Aphrodite, who was still understandably a little upset about the whole being-shanked-in-the-arm thing), so he traveled around the Mediterranean having all sorts of adventures. He ventured across North Africa, Italy, and Greece, built some cities, and then basically vanished out of history. No sources exist explaining what the hell happened to Diomedes, which is kind of interesting and awesome. Some mythographers speculate that he died of old age as the ruler of a distant land, while other folks are convinced that Athena granted him immortality and brought him up to live out eternity on Olympus. Dante of course claims that Diomedes and Odysseus are encased in a sheet of flame down in the Eighth Circle of Hell, but there really aren't a lot of non-Saints that Dante doesn't have burning in Hell.
Links:
About.com
Diomedes of Argos
Diomedes
Encyclopedia Mythica
Sources:
Apollodorus. The Library of Greek Mythology. Trans. Robin Hard. Oxford University Press, 2008.
Homer. The Iliad. Trans. Richmond Lattimore. University of Chicago Press, 1951.
Pausanias. Description of Greece. Trans. W.H.S. Jones. Loeb Classical Library, 1933.