>>42701678I was one of those people who always liked Stunfisk, I mad when it ended up on several "Most disliked Pokémon" lists. I can understand how not every goofy/ugly Pokémon can appeal to everyone, but Stunfisk is actually a based on a goofy looking animal.
I think a Pokémon that many passively acknowledged as bad, but have since pivoted on, is Mr. Mime. It was never really hated per se, since it is a Gen 1 design, but it was mostly the butt of jokes or accepted as one of the original weirdos alongside Jynx. Now it's the butt of jokes AND actually well liked.
Stufful and Bewear had a lot of backlash initially. There was a shift after everyone heard Stufful's cry, saw Olivia using them as a coping mechanism, and understood the joke of Bewear's appearance contrasting its strength. One of the most stark turnarounds was Delphox. Its initial leak caused a furfag mass suicide. Perrserker got a lot more fans after brief hate, I'm pretty sure the memes helped it. Of course, the Gen 8 fossils fall under this thread, except maybe Arctozolt. This is mostly anecdotal, but I remember people in my social circle just fucking hated Loudred. Now it seems like people like it well enough.
A Pokémon I think became LESS popular over time was Gallade. The more people acknowledge his hips, the less willing they are to think of him as cool.