There are various gigantic opponents you face off with in this game, some of them are shaped like humans and the others are monsters. The only common aspect is that they are ultra strong. Normal attacks won't even make a scratch. Yet all of them have weaknesses, unearth them and take advantage of them to deal killing blows.
Cooperating with fellow warriors is a very important aspect. Make use of the adhoc networking facilities to advance in your quests. There are two parts, the main quest and the free missions, no matter what you are conquering, always ask your friends in real life to help out in this virtual world. It's easier to take down a behemoth with two than just with one.