How do I, as an individual person, have the power to bring Moshiach?
If one evil person can unleash such horror, how much more can one caring person accomplish for the good?
In our generation, we have unfortunately seen abundant evidence for the reverse: One individual, inspired by madness, hatred or wickedness, can unleash horror and evil upon countless innocent people. A lone terrorist can blow himself up in a crowd and destroy hundreds of lives in an instant. Hitler, may his name be obliterated, was just one person, yet he incited an entire country to engage in acts of indescribable brutality.
King Solomon says in Ecclesiastes, "G-d created all forces in the world in perfect balance." G-d created day, and he created night. He created Moses, and he created Pharaoh. Every hero has a nemesis; every bit of wisdom is countered with an abundance of foolishness.
It often seems that the world is biased towards the darker side. This is only a perception, however. One hero can possess enough power to vanquish a multitude of villains. The insight contained in one line of Torah can be potent enough to counteract volumes and volumes of nonsense.
That's why it can seem that the forces for good are hopelessly outnumbered. G-d had to make their numbers few, just to keep things fair. It is our responsibility to view ourselves as a beacon of light in a dark world. We must not fall into the trap of thinking that our lives and deeds don't matter. In the words of Maimonides: "We must view the world as being in perfect balance... With one good deed, one kind word, or one good thought, one person can tip the scale and bring merit and salvation to the entire world."