[quote=CreedTheChimera]
I think he's talking about the Pandemonium event in the Grand Magic Games. Or maybe it is the Tower of Heaven, IDK ^^'
[/quote]

Well, on both fronts, Erza had difficulty. The main difference between those two fights was the quantity of enemies. I can't quite remember whether she fought against 100 or 1,000 enemies in the Pandemonium event...