Dark Souls and vicious, virtualized death -- you cannot have one without the other. Be it to a hollow with a broken sword, an ogre with a poisonous club, a territorial stone dragon, or the edge of a cliff; death is inevitable.
As you'd expect in any series brimming with boss encounters, some of them rise above challenging and take their place as ruthless, genocidal, power-tripping murderers. Except, with the Souls series in question, there are a ton of bosses that are more than capable -- and bored, even -- of smashing your face in for hours on end.
With Dark Souls 3 still pending international release on April 12th, I hand-selected 20 bosses from only the first two games of the trilogy. Bloodborne and Demon's Souls bosses were not included, though some surely would have made it.
The life-draining monstrosities to follow are only vaguely ranked from mildly demoralizing to controller-crushing overlords, so don't take their order to heart.
(P.S. Dark Souls: Prepare to Die Edition and Dark Souls 2: Scholar of the First Sin spoilers incoming.)