Who has Ash lost to?
In the case with Unova, Ash loses to Cameron, who not only had a freaking Hydreigon, Samurott, and Lucario (within the latter being able to best two out of Ash's six Pokémon and the former unexpecting evolving which allowed him to gain the advantage), but keep in mind, he's a complete idiot who brought five Pokémon in ... Who did Ash lose? Tobias beats Ash using only two Pokémon. You can imagine how this infuriated fans, especially since Tobias used exclusively Legendary Pokémon (Darkrai and Latios), which very few Trainers in the anime have.