虎の威を借る狐 (とらのいをかるきつね): a fox that borrows the authority of a tiger; small person acting arrogantly on someone else's authority; person who borrows the authority of another to browbeat others

a fox that borrows the authority of a tiger; small person acting arrogantly on someone else's authority; person who borrows the authority of another to browbeat others

The fox that walks ahead of the tiger and enjoys being feared. For anyone throwing around authority they have borrowed, usually their boss's.

The same saying in Chinese: 狐假虎威