Illusive Ambition.

Ambition can affect people in positive ways. But it can also be incredibly dangerous. Being too ambitious can lead to being destroyed by a quest for power. A great example is the leader of the Pro-human organization Cerberus, The Illusive Man (Real name Jack Harper). His desire was to protect and advance humanity as a species in competition with every other race. A noble goal, but he took it too far and became obsessed and over ambitious. He conducted horrible experiments and ended up doing more harm than good, losing his rationality and believing that the only way to keep humanity alive was to try and control the machines that were trying to kill us. This, ironically, almost led to our destruction. The Illusive Man is a perfect example of how ambition is dangerous and should be approached with caution.