There are many sides to Lady Macbeth, and although there are many more negative than positive qualities, I will try to list some of them nevertheless.
Negative: she is ruthless, and stops at nothing to achieve her goals. She wants her husband to become king, and isn't afraid to be an accomplice in a murder to get what she wants. She is manipulative, constantly controlling her husband to do what she wants him to do.
Positive: I'd say that in the end, one of her positive qualities is her guilt - she feels guilty for all the murders she took part in, which shows that she is human after all, with conscience. I guess that her ambition could be both a positive and negative quality, because she is very strong and powerful.