Kingdom Hearts II Is Kairi useless?

I think Kairi makes wonderful motivation for Sora in the first game. Not just that, but she also saves Sora in her plothug. And in the second game, when she should have been useless because of her seclusion on Destiny Islands, she manages to leave and get herself to the final world before Sora. Far from useless.

 

Read The Bloody Death Of Kairi. It will make you laugh yet reenforce your point.

Kairi's far from useless as she has her own keyblade now and was able to fend off heartless with NO TRAINING plus I have a hunch she's gonna be there with Sora, Riku, Aqua, Terra, and Ventus when they fight Master Xehanort.

 

I would hate to call Kairi a "useless" character, but she is a bit...defenseless.
Yes, she is mostly in distress throughout the games, but it gives Sora motivation to save her and persevere for his friends. Everyone is connected to Sora and by showing his selfless and heroic attributes, a plot device is set in motion. Whether it's saving the world from untold darkness or saving his friends, it's all to build character.
Essentally, I believe Kairi was developed for many reasons.
1) So there wouldn't be an all male cast.
-Organization XIII kind of pushed the envelope for male to female ratio...ok, well, there were only two females ((three if you count Namine)), out of twelve men. Sure, you may not care about it being a "sexist" game, but some game critics would. It's just a precaution, I suppose. To have a leading female character is also a way to balance out two headstrong male characters like Sora and Riku.
Kairi frequently states phrases that say "don't change..", "We'll be together everyday..", "I'll wait for you..", etc. These statements give the player a gravitation towards a goal and to remind them that they're really just trying to get back home. Getting stronger with the Keyblade along the way is showing how you mature as Sora.
It's trying to keep you connected with the character!
2) Romantic Interest
-Tetsuya Nomura stated that there are NO in-game relationships offically established, but there is evidence throughout the games that support a theory of love between Sora and Kairi. It's a very argumentative subject as you could also say they are simply close friends. I'm neither against or for Kairi and Sora as a couple, but it seems the most likely. ((Sorry yaoi fans!))
Maybe something will be established in games further down the line...
3) Keyblades, Princesses of Light, and Fighting...OH MY!
-Kairi can weild a Keyblade.
Her heart is pure and has no darkness, like Sora and Riku's. ((Even though Riku's grew temporarily weak and he surrendered to the Darkness, blah, blah, blah!)) When Namine was born, Kairi did not become an empty shell of a human, known as a Heartless. She persevered though what must be a dramatic and challenging strain on one's heart. To say Kairi is weak is a bit of an insult to her character. Why? Think of the way Heartless, even Nobodies, act.
They scourge and attack any being with a strong heart to collect them in hopes of attaining the hearts they lost.
It's an act of despiration to give themselves meaning.
And to have a fourteen to fifteen-year-old girl pull through such a transformation without having a lapse in heart is pretty dang impressive.
Kairi is one of the Princesses of Heart.
Again, this has to do with the pureness of her heart. SPOILER: Even Aqua sensed it when she met Kairi as a child in Radiant Garden, casting a protective spell over Kairi's charm. END/SPOILER:
Kairi is expected to maintain peace throughout Kingdom Hearts, and with that kind of responsibility on your mind, it may be a little distracting. I know I would be constantly worried about "un-pure-ing" my heart or something...but Kairi carries out life normally on Destiny Islands. ((Some may say she's too stupid to do anything, or that she's obvilious, but I say she is only being a kid.))
Fighting.
Alright, Kairi isn't the most skilled Keyblade Wielder in the universe. She doesn't flip, or double jump, or use sweet upgrades because she is not trained. Granted, Sora and Riku weren't exactly trained either, but over the time of the series, the boys typically had hands-on battle experiences.
Those experiences do count as training.
Kairi has been living on Destiny Islands, waiting for her friends to come back like they promised. Those are two completely different senarios. Instead, I like to think of Kairi fighting for her friends through her memories, not her Keyblade.
She was supposed to forget Sora, yet she retained memories of him when she and Riku would all play together, but she couldn't remember Sora's name right away. Kairi new there was a promise made between her and Sora that he would come back, she refused to go to the small island where they adventured until she actually remembered Sora, and she wanted them both to get home safely.
No, she wasn't physcially fighting, but she was still fighting for her friends in little ways.
I know most say she just did nothing, but think of it this way...
How could she fight for her friends if she couldn't even correctly remember Sora? Wouldn't you like to know who to look for and who to address if someone asked who you were looking for?
Selphie was obviously confused when Kairi spoke of Sora, so imagine every person who Sora helped, forgot him. Remember, Sora is tied to everyone. One way or another.
What would Kairi do? She would be aimlessly searching for a boy with no face and no name who promised her that he'd come back.
I don't really think her motives were at a loss, do you?

All in all, Kairi ((like everyother character)) can be viewed in whichever opinion or light you want.
This is simply my opinion and I'm not trying to shoot down anyone else!

Sorry it's so long!

 

Well if your buddy says Kairi is worthless and Namine is cool, perhaps you should remind him that without Kairi, there is no Namine.
I'd say that's worth something.