The Consensus on Dark Matter

The best example we have of where we use gravitational lensing to prove that there's dark matter is in a phenomenon that we call the bullet cluster. So this is despite what the name may have, you believe it's not a single cluster of galaxies, but two different clusters of galaxies that basically collided. They happen to be going at an extreme relative velocity to each other and one, the smaller one slammed straight through the middle of the other one. The stars are very far apart and the density of stars in space is extremely low.