Beatty is the indirect characterized as intimidating in "Fahrenheit 451". One example of this is when Montage and Mildred are afraid of Beatty:"Montag lay back against the wall and then slowly sank to a crouching position and began to nudge the books bewilderingly, with his thumb and forefinger."He was shivering and he wanted above all to shove the books up through the ventilator again, but can not face Beatty." This is indirect characterization because this doesn't came out and tell us spicifically that he is intemidating.
Beatty was directly characterized as captain. One example of this is when all the fireman were talking about a fire :"Captain Beatty there...."(Fahrenheit 451 pg.33). This is an example of direct characterization because the words are quoted by the characters in the story; the audience does not have to assume he is a captain.