Dishonesty/Lying
This should be obvious, but lying is rarely ever a good thing. Of course, while this is one of the most toxic personality traits one can have…one does not need to be “toxic” to lie. We often see this happen among kids, and it is usually done as a way to fit in with their peers. If there is nothing exciting about them, they need to come up with something to seem special. Hence, the reason for those lies.
Yet as we grow up, there is rarely a need to lie. Some might still do it if they have social problems, causing them to lack many if any friends. However, there are others who just lie for no real reason. It is part of their personality to do so, and that is when things become toxic. You also can never truly know when they are lying or telling the truth, making them incredibly untrustworthy. A certain public figure was known for this, making most dislike him because they saw through the lies.