In Shakespeare's Macbeth, Lady Macbeth is hard hearted to a certain extent. She is certainly ruthless when it comes to planning Duncan's assassination, as well as manipulating her husband while she tries to convince him to go ahead with the killing. Macbeth realizes this when he sarcastically says that she should be sure to have only male children, which implies that she is not fit to raise daughters.
At the same time, Lady Macbeth never really does anything. She is worried that her husband won't go through with it, but when she has a chance to kill Duncan herself, she can't because the sleeping Duncan reminds her of her father. She also has nothing to do with the killing of the grooms, Banquo, or Macduff's family--she doesn't even know about these until after they occur. Plus, she is driven to a mental breakdown by her guilt, and ultimately commits suicide.
In fact, Lady Macbeth suspects herself that she may not be as ruthless and uncaring as she hopes she is. When she pleads with the "spirits" to unsex her and make her ruthless and unkind like a man, she indirectly reveals that she is worried that she is not as ruthless and uncaring as she needs to be to carry out Duncan's assassination. And, of course, she is right to worry--when she has the chance, she is unable to go through with it.
On the surface, I would say that Lady Macbeth is as "hard core" as she seems. After all, this is the woman who pushes her husband to commit murders. As soon as she hears of the prophecy, she is all over the idea of him killing Duncan so he can be king.
But, on the other hand, her sins end up making her crazy. We can see her start to falter in this way when she herself cannot kill Duncan because he reminds her of her father. Then, later on, she literally starts losing her mind (the sleep walking and hand washing).
So if she were really hard core, wouldn't she be able to deal with all the killing without going crazy?