Of all manifestations of power, restraint in the use of that power impresses people most.

不懂这道题的思路。

我想这样写可不可以：restraint 和不restraint都有留给people映像的时候。前者如：美国总统华盛顿主动要求退位，不连任；后者如秦始皇等。

Yes, you are right and find the examples already. So you can do a case by case analysis in the issue.

One more thing, the "power" here does not necessarily mean "authority". You can also find examples in ordinary people.