Why does everyone hate either Sora, Kairi or Xion?
Anyway, on topic, I hate Demyx. He is lazy, annoying and cowerdly. During 358/2 Days, he keeps sending Roxas on wild goose chases. Fighting his water clones is such a pain. The only time it's possible to respect him is during his boss fight, where he is nearly IMPOSSIBLE to beat (and again with the water clones), and by then, you hate his guts because you what to get on with the game and you can't. And he is so freaking overated.