I feel like this gifset is a perfect four-part guide to what Cassian probably goes through every time he is ordered to kill:
1. Reluctance
2. Resentment
3. Resignation
4. ResolveOh my god, the A C T I N G
How does he even do that with his face? I mean, his expression barely changes, but he perfectly conveys all the different emotions you just described! 😳