Whitebeard is the world's strongest pirate—at least according to everyone who knows what they're talking about. He's supposedly the closest anyone's ever come to finding the One Piece, and back in the day, he and the late Pirate King Gol D. Roger were considered equals, having clashed numerous times.
His health is pretty rough these days. Nurses are constantly hovering around him, IVs in his arms, the whole setup—consequences of both his age and a lifetime spent fighting the world's most dangerous pirates. What's funny is that despite all this, he'll still chug rum straight from the barrel like it's nothing. It makes you wonder what he was like in his prime if he's still the strongest now.
When Shanks tries to send him a message through the young crewmate Rockstar, Whitebeard doesn't even bother reading the letter. He just tosses it and tells Rockstar to pass along a message: if Shanks has something to say, he should show up in person—and bring an expensive bottle of sake while he's at it. Later, when Shanks actually breaks through a blockade to meet him, Whitebeard calls him "boy," a casual reminder of just how much older and more established he is. There's something almost paternal about it, honestly.
Content compiled by AnimeList.moe from publicly available sources.
