Should I replace the bent Derailleur hanger? My friend (also on a bike) collided with me while we were riding together. As a result of the collision, I now have a bent derailleur hanger. Should I replace it alongside the Derailleur? 

The bike is a Carrera Vengeance
Yes, replace it. It's too bent to be straightened, or will be weakened considerably if it is straightened.