I say this a lot because it bears repeating: it often feels like the evil in this world, and all its machinations, are too big to challenge. That loss of control leads to despair.
But to reassert control, to do good that you can observe and take strength from: be a harbor for someone. Be a rock they can lean on, be a stick to prop them up, support them.
It is small, yes. It won't solve all the evil in this world, no. But it will help. It will help them, it will help you, it will help everyone, eventually.