ITT: Best evolutions in the series, I'll start

Voltorb -> Electrode
Krabby -> Kingler
Poliwhirl -> Poliwrath
Grimer -> Muk
Bramblin -> Brambleghast
Carkoal -> Coalossal
Bunnelby -> Diggersby
Dunsparce -> Dudunsparce
Chamander -> Charmeleon
Rhydon -> Rhyperior
Lickytung -> Lickylicky
Tangela -> Tangrowth
Vannilish -> Vanniluxe
Dragonair -> Dragonite
Sneasel -> Sneasler
torracat -> incelroar
Duskull -> Dusclops
Pidgeot -> Pidgeotto
Drizzizle -> Inteleon
Goldeen -> Seaking