The new Ethiopian UU..
In my opinion it's one of the strongest in the game, rivals that of a praetorian. I'll attach a screen shot of what I'm talking about.
In this screenshot of the Oromo Warrior notice it has Drill I, Drill II, Drill III, and Drill IV ... with only 5xp's.
4-7 first strikes.. at 5xp.. seriously, they were taking out entire cities without even taking a single point of damage it was insane, they never stopped to heal once, not to mention -60% collateral..
It's out of focus so just click zoom in once!