He's not evil but by all means a true bred Slytherin — "using any means to achieve their ends" e.g. wanting revenge so badly, giving Sirius and Lupin to the dementors didn't leave Snape the least bit reluctant.
Or, maybe its just his style with the gals
I mean, Lupin's hardly the chick magnet, is he?
I guess onli Sirius could match Snape's prowness, right LS?! lol
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"Longbottom, if brains were gold you'd be poorer than Weasley... and that's saying something."