There is no way to scale what is good and what is bad because every story has two sides so it all depends on from which side you hear it and having high moral compass is kind of considered as odd personality and don't be surprised if people think that you are crazy.
Actually, one single person can change the world, at least for a brief period of time. The thing is, I have noticed those who were able to change the world completely in that way (even though they normal people like you and I, were helped by a series of coincidences and turns of the life for them to reach a position of power).
In a low of ways, people like Adolf Hitler, Mao or even Stalin were able to change much of the world (not completely though) and someone would have said to them in their youth that it was impossible for them to change it.
Though, I agree with you that any attempt to change the world will find resistance because we all indeed have our own vision on how the world is supposed to be ideally, not even mention the religious instances on it.
A good example of the two sized story is what we are currently seeing with the war between Hamas and Palestine, both of them believe to be in the right, it depends who one listens to.
Nobody will ever admit to the the bad buy or their own life / history.