Charun
Charun was the Etruscan God of bashing idiots over the head with a hammer. Basically the myth goes that when you're getting ready to die this guy shows up and cracks you in the skull a couple dozen times with a gigantor mallet to finish you off. Once you're dead, his boss Vanth shows up and the two of them cart you off to the Underworld so you can spend the rest of your life either yukking it up with the virtuous souls (if you're lucky) or getting repeatedly beat over the head with Charun's mallet. Oh, I forgot to mention that Vanth is a hot topless winged goddess, so once you bite it you can at least think to yourself, "yeah getting my shit bludgeoned to death with a huge fucking mallet really sucked donkey balls but hey at least now there are some titties." Then you think it's all good, but if you were a douchebag to everyone while you were alive then when you finally get to the Underworld the titties go away and Charun comes back to spend the next couple thousand years smashing your soul with his hammer and completely wrecking your already-dead ass.
The guy is supposed to be like seven feet tall and cut like a lumberjack with eyes that burn fiery red, a bitchin' goatee, canine fangs, a vulture-like nose and blue skin that's more leathery than a hard-living, past-her-prime Florida stripper. He has crazy hair that, depending on who you ask, may or may not have been made out of LIFE FREAKING SNAKES that can also BITE YOU IN THE FACE. His main homedog and wingman is Ares, the God of War, which is pretty badass company to keep. Back then they would just travel from war to war kicking asses and pounding heads like Tango & Cash or Maverick & Goose. Throw the half-naked Death Goddess Vanth in the mix and this was definitely one crew you didn't want to fuck with if you were some punk Etruscan chump.
The Etruscans would also paint pictures of Charun in the tombs of the deceased, just in case you managed to wake up for some strange reason. That's hard as nails. It's like, "yeah I kicked your ass once and I'll do it again motherfucker, so you better just stay dead." What's even better is that when THE POPE dies they tap him on the head three times with a tiny silver hammer, which is a ritual that was passed down for thousands of years dating back to Charun and the Etruscan times. So even the Pope recognizes the bitchin'-ness of Big Blue.
Not much is known about Charun, but I personally find it difficult to debate the badassitude of a Death Demon who's sole purpose for existence is to bust peoples' heads with a giant two-handed warhammer.
Charun: I heart smashing faces!