I'm assuming this is a good guy?

The best thing you can do is prevent yourself from running into this mistake by making characters this crucial tried and true. There's nothing wrong with experimentation, but it's wise not to take too many chances with a character that's carrying your RP.

The next best thing you can do is rework the character. Figure out what makes him/her so despicable and find creative ways to change it. If the character is too strong, make something weaken them. If their personality sucks, make something happen that changes the character's view of life or themselves. It's hard to say exactly what will fix your character, and you may need several events to get desirable results.

The third thing you could do is just suck it up and kill/remove the character. Make the legend actually refer to a different chosen one, make their soul bound weapon bindable to his soul mate, or whatever sort of BS that needs to happen, just do it! If the character is so bad that even you hate them, maybe your fellow players will be able to overlook whatever strings you have to pull to remove "it" from their world.