My least favorite is probably Litten. There's a story that goes with it, but i'm too lazy to type it out. Plus, incenaroar is the most terrifying of the anthros imo.
It's just an opinion of mine though.
i love cats so I think litten is adorable personally! and incineroar may have been near the bottom of my list if you were asking this question 2 years ago, but I got more attached to him after seeing him in the anime. kukui's was really cool!
i dont really have one but if i had to pick one that doesnt interest me much as the others.. i guess Tepig?
i also only played up to X and Y, i have the other games, just haven't started them yet so idk the ones past that...