Let's begin by defining what a leader is. A leader is someone who supports his/her subordinates in all possible way so followers can be engaged to the goals. Now, there are positive and dangerous leaders. These are three ways both kinds of leaders use their leadership to achieve different goals:
1) They use their authority to impose their point of view regardless of what others think. This is dangerous.
2) They know their influence to get know their team in all aspects. He is very well aware of their team's weaknesses and strengths. Therefore, he will make educated decisions on assigning tasks to achieve their goals. This is positive.
3) They are willing and determined to destroy others who may be on their way just to get what they want. When I say destroy, I mean they might undermine someone's integrity to get rid of him/her.
Now, dangerous leaders do have their own goals. Most of the time, such goals are connected to their own interests. Thus, this dangerous leader will try to do anything to achieve them. For examples, they might badmouth others, make up toxic stories about colleagues. They could even damage the team whole image and blame on them just to get what they want.