Narga (ESPECIALLY Silverwind), and Tigrex are both like, big faves in terms of flow. But all time king is Velkhana. It’s such a spectacle even if it takes two minutes to get into melee sometimes.

Fighting Velkhana feels like a dance sometimes and thats amazing. Flow is a very good term, as you said, and Velkhana's fight reminds me of a game of rhythm because of that: if you flow with the monster, you will win; if you lose the rhythm, Velkhana will make you dance the song of ice and death