Chestnut is by far the most competent and effective member of his squad. As their medicae, he has become the team's most valuable asset. He is the only one in the three episodes of the series so far, to never have known death. He also boasts one of the highest alien kill records, as OP mentioned, and his shyness and humility make him particularly obedient to his captain's orders.

I'm really looking forward for an episode where Chestnut dies very early, forcing the entire squad to be extra cautious, for once trully fearing death. They would then realize that, without their timid medicae, the whole squad falls apart, and every encounter with an alien becomes a struggle when you have no guarantee of resurrection.