My Bloody Valentine. This episode explained a lot of the back story as to the hatred between the PLANT/ZAFT and the Earth Alliance. Basically the Earth Alliance destroyed a PLANT colony, killing over 200,000 coordinators.

Rau and Athrun testify before the PLANT supreme council about the destruction of the neutral Heliopolis colony, ultimately laying the blame on its destruction on the Federation. The council then debates what the best course of action is. While this meeting is taking place the Archangel goes to steal supplies from the debris zone that once was the destroyed colony. The display quickly cuts between three scenes: the meeting of the PLANT supreme council, the Archangel crew getting supplies and a flashback to the destruction of Bloody Valentine.

The episode ends with Kira destroying a ZAFT mobile suit in what I believe to be his first taking of life.