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Complete a level with a single swing while collecting all stars in region 6.

As the description says, with a single swing you need to knock out every enemy in the level and collect all three stars. The first level in region 6 is good for this, and there is a video below showing how it's done. Be warned that the shot in the video is extremely precise and difficult to get exactly. I tried for at least 15-20 minutes making very miniscule adjustments to try to replicate the shot in the video. Just stick with it, and try every shot at least twice before adjusting, because the ball may go slightly differently and that could make all the difference.