Wigglytuff is a tragic case of its pre-evolution being far more popular than its evolution. It's very similar to Raichu in that sense, because Jigglypuff and Pikachu are part of what could be seen as the "Mascot" Pokémon for the entire franchise, while Raichu and Wigglytuff just get left in the dust. At least Raichu gets an Alolan form, but Wigglytuff was just given a Fairy secondary typing, with an expanded movepool, and that was it.
That's not to say that Wigglytuff doesn't have the right stuff to be used in battle of course. Wigglytuff has a huge moveset thanks to its normal typing, and with its massive HP stat it has a chance to set up some moves before it’s eventually taken down thanks to its low defense stats. Still, Wigglytuff is one of those Pokémon you can try a couple of different things with to see what works for you as a trainer. While it may not be the most popular puff, it's known to have the stuff to be tough.
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