Neji goes to explore the biomes very often, bringing food to the Pack as it is his duty to feed them as a leader. The Hyuga used to be experts in battling, and he was its genious- it's not a surprise that he can defeat almost any enemy that crosses his path.
He died fighting the Nine Tails Fox, who still lurked in the rainforest even all those moons away- both lives were lost that rainy day, and Kakashi was the next Pack Leader.