Annihilate for 5k? On a zero expertise target maybe.
I hit it for 4K + on almost every crit and it crits often. Most are around 4500 but definitely on a squishy target or a low expertise target 5K crits are more than possible. And this thread is about 5K capable abilities.
Of course I'm near min/max right now, but I'd say I hit a 5K annihlate about 5-10% of the time.