I do not hate any of Ash's Pokemon but there are few I dislike.
- Donphan; Although I liked it as a Phanpy, it lost most of its personality traits after the evolution. And I do not like Donphan as in general.
- Infernape; It is mainly due to hype. Also I never liked its personality.
- Gible; Just coz of Draco Meteor actually.
- Unfezant; Freaking outs...
- Oshawott; No further explanation needed.
- Fletchling; Still early to talk probably. But steals food, leads you to a Beedrill swarm and laughs at you, then suddenly a cutie. I wonder when was the last time Ash was positive towards a food-stealing Pokemon... I hope the writers keep this Fletchling like Unfezant. I would hate it if it reaches Pidgeot/Swellow/Staraptor level.
Since Fletchling is shown on the most recent episodes, me disliking it is more fresher than the others.