Hey there!
My idea behind this is that fear can lead to someone being in an upper-hand position against someone, leading to them being more "powerful" than that person. Sometimes, people can take advantage of others to show their dominance. Others will lead their countries by making their population fear consequences if they don't follow their commands.
Power and fear can be used for good, especially in the case of being president of a country or something similar. For example, one could use their powerful position and can make citizens of their country fearful of the consequences of having bad health and not getting exercise. This might motivate the citizens in bad health to start changing their diet and exercising. However, power and fear can also be used for evil in this case. One could overpower the word of their citizens and establish that, if they don't follow orders or try to question their authority, there will be consequences.
So, a good thesis behind this could be:
"Fear can give someone varying dominance over others; it is up to the person in power to then use it for good to encourage positive change in those they lead or for evil by bullying and creating a hostile, one-sided relationship between them and who they control."
Hope this helped you out! :-)