He’s a Pirate
First and foremost, Edward Kenway may be the coolest Assassin of the series simply because he’s a pirate. While he does join the honorable order of Assassins at some point, Kenway is first and foremost a pirate, and that’s present in everything he does. He’s always looking for a big score, and always obsessed with treasure and profit. Kenway started out as a privateer for the Royal Navy of Britain, before the life of fame and fortune lured him away.
Kenway also puts the best of both worlds to use as he pillages and plunders vessels from both the English, Spanish, and more. Even after his intentions become a bit more focused, Kenway never drops some of his pirate-like tendencies. He’s certainly the most swashbuckling and over the top of all the Assassins, even in the face of characters like Ezio and Jacob.