(as) black as (one) is painted
As evil, malicious, or malignant as one is described or believed to be. I wasn't sure why everyone is afraid of the old hermit who lives on the edge of town, but after having a few conversations with him, I found that he is as black as he's painted! The biker gang plays up its tough demeanor and hellish reputation, but they're really just a bunch of regular guys and not as black as they're painted.
*black as one is painted
as evil as described. (Usually negative. *Also: as ~.) The landlord is not as black as he is painted. He seems quite generous to me. Young people are rarely black as they are painted in the media.