Level 55+ Spearazon (~1900 hit points, supermax resists, 15K+ defense), killed by Normal Baal AFTER BAAL WAS ALREADY DEAD (see screen shot) :
Pounced on top of him (had full Pounce "Fury" bonus on), stabbed him with "Great Hunt", he went down in about a second and a half, was just about to talk to Tyrael when his black pool of death appeared beneath my feet and one-shotted me far too quickly to drink a potion, to move or to do anything. This was AFTER Baal was clearly dead and his corpse lay splattered beneath the pillar that you see in the above screen shot.
Ironically, after I hit "Escape", it presented me with the following congratulatory screen :
So let's consider this, Median players : you can be one-shotted by a boss monster even after you have killed him, despite the fact that (unlike, for example, Andariel's Meteor Shower) he did not appear to initiate any attack on you prior to being killed.
In Median, even dead monsters can kill you without warning.
Nothing "unfairly hard" about THIS game... right, folks?