"Of all the manifestations* of power, restraint in the use of that power

According to the narrator restraint in the use of power impress people rather than manifestation. I believe that the use of power is completely depends on what situation is demanding. It's the behavior of every creature on earth that powerful creature dominates on weaker creature. sometime manifestation of power could be key of survival where as restraint in use of power could become key of survival. So therefore; I would agree with narrator in some scenario where as disagree in another scenario.

It is very important to use the power where it is required. If you failed to do so you will become a loser. For example in boxing ring if a fighter does not fight against the competitor and does not manifest his fighting skill he could lose the competition.

On the contrary powerful weapons such as nuclear bombs which are created to use against enemy during wars must be restrained, because if any country try to misuse there powerful weapon against their enemy country could lead to destruction of the whole world. Therefore, in this case restraint use of power would impress most people.

In conclusion, manifestation or restraint in use of power depends upon the fact that what is the demand of situation. If not done so, attaining power would become meaningless in the world.

According to the narrator, restraint in the use of power impresses people more than manifestation of power.

I believe that whether the use of power is appropriate is completely depends on what the situation is demanding.

If you failed fail to do so, you will become a loser.

In conclusion, whether power should be manifested or used with restraint depends upon what the situation demands.

Practice these sentences 10 times each so that you develop the habit of using correct English grammar. :-)