When I killed Ishtar on my first try with a crit. It was really anticlimactic, and I laughed a lot.
My second is when you you go to the Western Isles in FE 6 with no real reason(My translation patch when I first played it didn't give me any context), I was ready to get really mad and annoyed thinking that, "this is stupid, this is just to make more levels and drag out the game, this probably has no bearing on the story." Then after I finished getting annoyed and started the next chapter Roy basically said that it was stupid and he didn't see a reason for coming here. I was dumbfounded, I didn't think they were going to address it. I thought all the characters were just going to carry on and drag out the game for the sake of added more content that has no substance, and then Roy calls them out on it. 10/10. Then they actually explain why they are there and it makes sense(somewhat).