Straight up visual first impression, Hive. No doubt. They're skeletal beasts with either 3+ or no eyes. And they wither away on death. In long term however, Vex takes the lead. How do we currently fight an enemy which can travel in a space-time dimension with technology beyond our knowledge. And then the simple shock of seeing a robot-like creature with only an organic core, which many believe is the tip of evolution. Outclassed, outgunned and outsmarted.