I would think that for some people it is. It depends on how empathic you are, and even then there are probably other variables that contribute to whether you're able to tell specifically from the eyes. But I think it's problematic to categorize people as "good" or "evil" in a binary way. Nobody's 100% evil, and nobody's 100% good. And evil is fundamentally a subjective assessment. I think it would be better to say that some people have a foreboding/ominous characteristic to their eyes, or that some people are sadistic, narcissistic, sociopathic, or wahtever.