(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. I really doubt that Amanda is behind this heinous prank. I've gotten to know her pretty well, and she's really not as black as she is painted.
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