Andrea Hess wrote a 3-part series of in-depth posts that I find illuminating and provocative: What is Negative Energy? Who Are Negative Souls? and How to Deal with Negative People. Each post builds upon the other, and I'd recommend you begin your reading with the first post listed.
Andrea points out that negative souls aren't necessarily evil. Some look kind and seem to say the "right" things. She asserts that many people on the planet do not fit exclusively into the category of "lightworker" or of "negative soul," but work with either energy based upon convenience at particular times (free will). However without choosing a definite path towards the light, life remains stagnant and little changes.
What if you suspect you have negative souls in your life? As you read over Andrea's list of 11 defining characteristics, you may recognize friends, family, or work colleagues. I found myself struck by several of these clues: negative souls don't create anything, since creation is an expression of Divinity; they have a way of causing us to doubt and question ourselves; they show up when we are down, but not when we are happy and connected to our purpose.
In the 3rd part of this series, Andrea describes 7 strategies to deal energetically with negative people. These strategies reflect a spiritual depth that goes beyond the typical "how to" list in popular magazines. She concludes with the reminder that it is not our job to "save" negative people. What a relief. That's one less thing to feel guilty about!