I'd have to say the best moments was when Shanks and the Red-Hair pirates become big damn heroes, ending the war with words
Mihawk basically saying, screw this I ain't fighting Shanks, in his own way
How Luffy came back from his despair caused by Ace's death, by remembering his crew
And the look on everyone's faces when their captain says he wishes to tame the Krakken, and does…
The worst moments would have to be when even after the war ends, the three admirals continue to fight, and all to uphold Absolute Justice. I don't care what people believe, but that isn't Justice, no matter what people say.
Also how it was said that nobody would help Tiger Fisher. I don't care what anybody says, someone must have tried to help him, but was probably shot by the Tenryuubito before anything could be done. Like all history this part may have been left out