To be precise, Urshifu VMAX and Mew VMAX were near the top for most of their lives, and Rapid Strike Malamar held on for a solid year. Limitlesstcg seems to say that Single Strike Urshifu VMAX was generally the best Single Strike deck in 2021, but from just reading Pokébeach's articles program as a recent researcher of competitive Pokémon back in the day, it felt like Single Strike was playing hot potato trying to figure out what it's poster child would be.
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Yep, this basically sums up how I saw Single Strike. (Although by the time we got to the bottom right two items, I wasn't thinking nearly as much about the rest of the chart and probably would have looked up the decks on Limitless before assuming they were all viable.)