Just going to duck out of this thread because I don't want to get pissed at a few choices, but here goes;
Besides obvious issues, like Goku, my Least Wanted characters list starts with Sora from "Kingdom Hearts" due to the fact that I feel it would open the doors (no pun intended) for Disney characters to appear, and then giving Goku supporters more fire in their justification in putting him in, which in turn, would lead to any yahoo requesting dumbass choices like Rick & Morty (which I had a nightmare about a few weeks ago), Darth Vader, or Batman. I don't like sounding old timey about things, but this is supposed to be a celebration of video games, not a celebration of popular culture. Especially things that are likely going to be flash in the pan.
Very close second is Phoenix Wright. I might be the only hater of Ace Attorney, and that's largely due to me going from not understanding the point of the series to realizing just how stupid it is and how all-over-the-place it became. Like, I can get every major antagonist being a prosecutor given the Japanese court system, but the settings and the characters just become so godawful, I just can't deal with that franchise. Hell, Phoenix is my punching bag in UMvC 3.
Third would have been Krystal, but she's an AT, so whatever.
Prior to Ultimate's Everyone Is Here announcement, fourth would have been Pichu, but I'll live with it.
Fifth on this list is anyone from Kid Icarus not named Medusa. I largely attribute it to me not liking Uprising at all, but I believe you should give priority to Medusa before you give others an opportunity just because.