Satan grant me the power to understand this entire thread...
...If you want a more objective opinion:
Itoh isn't the worst written character in the game but he is far from the best, he serves as a side character in this case, much like Booster, but only exists for a brief period of time in a single quest. He is an important character to the lore nonetheless, if there's any characters you should hate with good reason, it'd be the antagonists of the story, as they are intentionally written to be people you couldn't show remorse for because of their actions, be it them murdering Arthur or sending you to the labyrinth to do their bidding.
If you want to say that Itoh is the worst character in the game, that is simply untrue, as there are much worse characters that exist within the story itself, and if you want to speak from it in terms of how they are designed, the villains are actually the best in the game, with the most fleshed out backstories of all of the characters. The island is small enough for Itoh to be able to trust someone, especially with the fact that the alleged letters on Quote's cap are from the language they speak on the surface (Presumably Japanese in this case) and thus would allow the humans to dictate that they are one in the same. That is why Kazuma and Booster are easily able to trust the player.
Antagonizing Jenka is a poor decision to make, considering she is the person with the most power over the island, next to the core and her brother, Ballos. She sent Quote on the fetch quest because Pixel needed to pad out the game to make it feel more open world when in reality it's very linear to dictate his ability, she likely very well knew of the location of each dog, and may have also known that Quote would come too. It is possible that Misery's birth name wasn't Misery, but her own chosen name, be it given to her by one of the Demon Crown bearers or otherwise. Giving monsters names levels them up, right? I saw that in an anime.
Less integral characters like Jack, Mahin, and King exist because well, a village isn't a village without people to live in it, would you much rather explore a desolate wasteland with nobody to talk to than a vibrant town with simple but memorable characters? Next time you make a joke thread make it more challenging to argue against.
Each character has their own ambitions, you need to take that into consideration.