It's Sabo. Ever since it was revealed that he has been alive, I've been dying to see this guy fight. The fact that he's brothers with Ace and Luffy and went through the same childhood hardships as they did made me so curious to see how he fights because those two turned out incredibly powerful.
And it is BEAUTIFUL. Because he didn't mature with a Devil's Fruit power, he had to learn how to fight the old-fashioned way: good old martial arts. Add Ace's Flare Flare Fruit into the cauldron and you got yourself a awesome fighter potion. He sent Burgess's "WEE-HAHAHA" ass flying in one hit. F*CKING BRUTAL. This kid has already become second-in-command of the Revolutionary Army--who as a reminder, Luffy's DAD is the head of--WITHOUT a Devil's Fruit power. So how much is now having one of the strongest DF powers gonna elevate his game? I guess we'll have to wait and see.
But yeah remember this Gajeel-Kenpachi mix looking character? That's Luffy dad, the Master of Wind and Storm, Monkey D. Dragon and leader of the Revolutionary Army. Which also means he's the ONLY guy in the Revolutionary Army who's stronger than Sabo which says a lot for Sabo's power. I can't wait to see his true strength.