Just like the Pop Culture Moment, this is tough. Castiel had several, my favorite being him taking out all those demons with a sigil carved on his chest. How brilliant! When Cas goes into self sacrifice mode, he's one scary ass mother****er. Sam also gets an honorable mention for his calm yet cold systematic killing of a bunch of Croats one by one in"Two Minutes To Midnight," not to mention his rescue of several innocent bystanders in the process. No wonder Bobby was impressed enough to believe he could take on The Devil. Raging Sam is creepy, but cool yet deadly Sam scares the crap out of me!
The most satisfying Badass Moment though comes from Dean. By the time Zachariah had gotten to "Point of No Return," the dude had just gone too far. Most demons were less evil and diabolical than this misguided angel. It was clear by that time he had to be stopped. Still, we didn't know Dean had the type of power to do it. We didn't know Dean could hide an angel killing blade, strike the balded one through the chin and watch without having his eyes burned out. It's a mystery that went through the finale without resolution, but I can live with that for now because the moment was so awesome. Dean once again shows people how killing the bad guy is done.