Pre prequel Boba. Hands down. Back when he was a gravelly voiced, spurs-wearing, BAMFer who took on and teamed up with Vader more than once. The comics did a bang-up job of really fleshing him out and giving him some awesome adventures. A major favorite being Twin Engines of Destruction where he sticks it to Jodo Kast. He's the original. As I like to say he's the Wolverine of the Star Wars Universe. A one-man army who faces any and every kind of danger, cheats death, and walks away on top. He's got the Solo rivalry, all the other prominent hunters after him, the mystery, the legends and ghost stories, the gadgets, the ship, and no one knew what he looked like or who he really was. The galaxy wasn't over run by Mandos, and Fett was a VIP wherever he went. He was just as deadly unarmed and unarmored as he was fully suited up. That's how Star Wars was supposed to be. He was never a whiny little brat who stole his father's shtick and who was the same guy as the millions of troops the republic churned out. In that continuity everyone would know who he was and they'd have killed him long ago. Besides his father never even got to train him. As Harry Osborne knows, the gear does not maketh the man. He tried to fill his father's Goblin boots but couldn't hold a candle to old Norman.
Old School Boba Fett. Like Chewie it would take something like an entire planet falling on him to kill him.