It's hard watching someone close to you die, especially after you had been talking to them just moments before, and they seemed perfectly fine. Is Oliver going to keep Laurel's promise? Is that what he's contemplating now as he looks over her dead body?
How many pictues have we had of Oliver in this position, good facing evil? He's been there against Slade, Malcolm, Ra's al Ghul...yet he always comes out the victor. Damien Darhk should just pack up and leave now.