Lord Sam Sinister

Lord Sam Sinister was a character in the Adventurers theme. He was formerly know as Baron von Barron and is the main enemy of Johnny Thunder and the other Adventurers. He has a sister named Alexis Sinister. His name was changed in the Dino Island theme. He also appears in LEGO Racers 2.

Lego.com Biography
''Lord Sinister is Johnny's arch enemy. He is selfish and evil, with no limits to his ambition or greed. He has a huge private collection of ancient and valuable treasures from around the world and is always on the hunt for more.''