What level are you on in Showdown? I finished and got all of the five badges, but then I deleted my progress and now guess what? I'm at level 19 and it is SOOOO hard to fight on a slope (when you get to the bridge across the water to the castle's inner courtyard). Combine this with the brown armor Mii rivals that literally have the most unpredictable moves, and sometimes swinging on the bridge will actually miss the Mii. That really makes me sad, it took at least 70 tries to get through untouched. It is almost impossible to get the perfect combo, as well, but I have gotten a 70-hit combo in the Normal Volcano level. You see, usually, the easiest stamp to get in the Swordplay category is the stamp that requires you to complete a level, keeping all of your hearts. It can be earned literally on the first level, as there are no hard enemies (besides Cole) and everyone is slower than Christmas to attack you.
On a side note, It was pretty easy to pass level 10, as it took me like 20 minutes. Then completed Showdown altogether in around two hours. It's great because my fitness age is 23. This means that I have the fitness strength of the average 23-year-old person. Now, I don't actually know what Fitness Age is, so I can't really say what I feel like.