... TOO MUCH CHOICES! You're asking me to choose between my best friends and my waifus! WHYYYY
I'll list the characters I don't like (that have actual names and portraits), because it's an easier question.
P1:
-Reiji Kido. Too much of a hassle for not much of a good result. Personality wise, he's good though.
P2 IS:
-Hmmm... No one.
P2 EP:
-Tatsuzou Sudou. He's just an old cult leader. There are way better characters in every single game.
P3:
-Kenji, the magician SL. Simply because I don't want to be friends with a milf hunter whose personality is just that.
-Bebe, the temperence SL. Mostly because he's an annoying weeb, annnnnd I'm French.
-Nozomi, the moon SL. He's the only one of the three whose link I haven't completed... Because he's an asshole.
P4:
-Ayane, one of the Sun SLs. Mainly because Yumi is way more interesting and doesn't look like an alien.
-Hanako & Kashiwagi. They're dumb, they're obnoxious, and I actually think I liked King Moron more because of HIS antics.
P5:
-Kaneshiro, but only because he's not as memorable as the other targets, despite being the point where Cerebus Syndrome kicks in for major ennemies.