One moment that had a kind of impact on me was from Til Death Do Us Part. After Weyoun wakes Damar up and Damar can't look at himself in the mirror.
The thing is, it's so cliched that it really shouldn't have worked. But Damar looked so lost and vulnerable in that moment that it actually made me worried about him even though I hadn't given the character a single thought before this. I became intensely interested in what was going to happen to him. Fortunately he had a great redemption story that grew from this moment.