RDA 2nd zone
You will come into contact with a Hammerhead creature here. He is fairly easy, just make sure you use your skills and dodge ability. As long as you keep moving he shouldnt do much harm. The majority of this zone is finding crystals that are displayed on your map. You will encounter lots of Na'vi warriors and Viperwolves while travelling throughout this zone.
At the very end of this zone you must face a Na'vi Commander Beyda'amo. He is tough so don't get too close. A few rounds of your grenade launcher should finish him off easily.