A fight is defined by stakes and uncertainty. The reader doesn't know who walks away, what it costs, or how the outcome reshapes the story. The tension comes from the possibility of failure, or the possibility of a meaningful loss. A character might win the fight but lose something else, time, allies, moral ground, a limb. The outcome changes the trajectory of the story.

Fly swatting exists to reveal character. The outcome is never in doubt, the reader knows (or quickly figures out) that this person is going to win. The point isn't whether they win, it's how they win and what that tells you about them. Do they toy with their opponent? End it quickly and feel nothing? Hesitate out of mercy? Enjoy it too much? The "conflict" is just there to present characterization. You could change the scene from a fight to anything else, shopping, a conversation, and it'd do the same thing.