Curse of Hatred
From Diablo Wiki
Curse of Hatred is a spell cast by some monsters that increase the damage of their attacks but also yours (v2.05). There are two ways to see if you are affected by this spell. First, there is a little icon above the "Achievements" icon in the menu bar that appears. Hovering over this icon tells you how many seconds are left before the spell terminates. Second, when you are under this spell, there are dark stripes appearing above your head. One of the monsters that uses this spell is Diablo.