@Legion-114 Yes, the Dark Angels were founded by Lion El'Johnson. They are the first legion, the Unforgiven is the name given to them and Chapters that use the same Gene-seed. The Dark Angels and all of it's successor chapters believe themselves unforgiven for the crime of what happened on Caliban. The successor Chapters all stay in close contact with the Dark Angels making them secretly a much more unified force than most Chapters.
I would think Lion El'Johnson would act as leader to his chapter as well as the other unforgiven. Making them a force of the Emperor's will.