I think most underrated pokemon are 2nd evolutions from the starters like charmeleon,wartortle,croconaw,Bayleef (best),and marshtomp i think bayleef is underrated but i like him cause his looks not cause stats and moves!
One of my favorite Pokemons has always been Pincir and nobody seems to like him as much as i do :c he's a beast and has great stats, and he looks so badass too
I agree Raichu is always overlooked compared to Pichu and Pikachu. I always have a Raichu in my team plus he can learn Giga Impact and Hyperbeam which ia a bonus.Raichu, he gets so much hate because he is an evolved Pikachu which apparently 'doesn't make pikachu cute anymore'. I've always preferred raichu, he is so much cuter he just has the unfortunate role of being the one to rid pikachu of his majority favoured 'cuteness'.