Manfred has been dubbed a Byronic Hero because of his characteristics and background. How does one of Manfred’s Byronic qualities dub him the hero?

Of the many Byronic Hero qualities in Manfred, the sense
of distance and alienation he displays throughout the narrative is what helps to make
him the hero in this story.  Byron is fairly confident in constructing Manfred in a
manner where his estrangement from society is his defining element and one that makes
him the ultimate hero.  His refusal to accept help from everyone and anyone is what ends
up forming his final stand, in which death is the only element that can conquer him. 
This is a deliberate statement on Byron's part about Manfred and the Byronic Hero, in
general.  For Byron, the world of "mere mortality" will be unable to fully understand
and grasp the level of genius, austerity, and intensity of the Byronic hero, of
Manfred.  Not even immaterial spirits can reach him, as Byron strives to display Manfred
as the tortured emotional genius who possesses more insight into his own emotional
character than even the spirits can grasp.  It is here where this quality ends up
defining Manfred throughout the work, creating the ultimate showdown where death is the
only force that can conquer Manfred, permanently excluding him from a society that is
too feeble of mind and spirit to fully understand him.  This is the vision that Byron
hopes to convey through his hero and his relationship with the
world.