Sure, there are the usual arguments for opposing her: she's never accomplished much in her long life, never been a leader, never been an effective head of an organization of any import. All that's true, but that's not the worst of it.
When I think of Hillary Clinton, I think of an arrogant, angry woman with a superiority-complex, looking down her nose at the little people, all with a scowl on her face. Rules do not apply to her, they are for other people. Facts don't matter, only spin. Even if I agreed with Hillary philosophically, I would find it impossible to like her personally. It seems to me that her whole existence on this planet, her every waking moment, is suffused with one burning agenda: to rule the masses, the masses whom she hates, and for whom she feels only contempt.
That, in a nutshell, is how Hillary Clinton seems to me.