Sunohara taking on the entire soccer team back he was a freshmen. Talk about Badass Decay...
When he pulls a Big Damn Heroes to save Mei from that same team, it's even more awesome.
Tomoya earning his happy ending at the end of After Story. After going through hell, having his wife and child die, all of the good things that he did before come back and reverse time so he can live happily with Nagisa and Ushio.
How about Tomoya fighting a gang leader and not only holding his own, but actually getting hits in and practically ending it in a draw? He might not be as proficient of a fighter as Tomoyo but he's still pretty damn badass.
Still, it's undoubtedly Yukine who earns the awesome award for that episode, as she succeeds in preventing a battle between the two gangs.
Nagisa gains one of her own in After Story, when Tomoya is having a massive Heroic BSOD in which he's punching a wall in anger over losing a good job chance since his dad has been sent to jail... and not only she gives him a Cooldown Hug, but she manages to pin him to the wall to stop him from harming himself further, nevermind that Tomoya is taller, physically stronger and quite healthier than Nagisa and not exactly in control of himself... Therefore, it's a big Take That to those who accuse Nagisa of being a weepy and whiny wall-flower. Sheisn't. And she definitely earned the marriage proposal that followed.