Bob is of a different species that is larger than the species of the subordinates
The subordinates are scared of Bob because he's so big. So they do whatever he says.
Bob is able to buy more food or afford fattier food than his subordinates, making fatter than them.
Inverted: Bob is shorter than his lowers-in-command.
Subverted: Bob was actually under mind-control by a very small person...
Double Subverted: ...who, in turn, is revealed to be controlled by a giant.
Parodied: All the organization members' heights are measured before their joining. As soon as someone is found to be taller than the leader, the latter is stripped of his rank and the new member takes their place.
Zig Zagged: Bob is huge, but, when he is killed, it is revealed that a 2' man was operating him from inside his torso; he was an android. However, the "dwarf" reveals that he had shrunk himself in order to control the android, and quickly reverts to his actual great size. However, it is later revealed than he, too, was under the influence of a very short person, but it is later revealed that the masterminds behind the plan are actually shapeshifters who can change their height at will.
Averted: The leader is no more physically imposing than any other members of the organisation.
Enforced: "We need an easy way to make Bob stand out from the crowd and also make it clear that he is the boss."
Lampshaded: "I know that my being seven feet tall has nothing to do with my leadership skills, but..."
Invoked: "I'm going to eat well so that when I grow up, I get to be big and become the leader."
Defied: "No, no, no. Don't think that just because you're the tallest you'll get to be in charge of this team."
Discussed: "See the big guy in front? He's obviously the leader. Shoot him first."
Conversed: "You know, it's always the largest ones that order the others around..."
Deconstructed: Bob's size is the only trait that his subordinates see in him, and he subsequently grows depressed that he is looked up to only for his physical prowess.
Reconstructed: However, his size, coupled with a cunning strategic plan of his, saves the day, and so his other skills are also acknowledged.