Look to the history of the world. Nearly every single awful tragedy in our world has been motivated by (from the perspective of the person doing such actions) good intentions. The grand utopia said villains had in mind when carrying out their misdeeds never came to pass, but the horrible actions done in the name of it most certainly did.

You cannot predict the future; your actions will often have consequences far outside that which you intend. And there's an extremely good chance that what you intend to happen will never happen anyhow! This ultimately makes Machiavellianism somewhat of a non-starter. The ends cannot logically justify the means when you cannot even truly know what the ends ever will be. All you can be certain of is that we will experience the "means."

Make the world as you would have others make it for you.