The gigantic sword is just so stupid that Cloud loses al credibility immediately.
Just because you deviate from the fact that most people think Cloud's unrealistically large sword is cool doesn't mean that it's stupid, and it doesn't jeopardize or have anything to do with anything about him as a character.

It's unrealistic in comparision with the insanely unrealistic content of the game.
Realistic, sure. The series isn't called Final Reality.

Because cloud is the unlucky loser who artists wanted to carry the sword, he becomes one of the poorest designed characters in video game history.
So his large sword makes his character design... Right... So what does he become when he equips the Murasame? Then he's cool by your logic, right?

Backstory doesnt save him because similar stuff is found all over the world in all kinds of stories.
What?

Thus: The only original thing about Cloud is this massive sword. But the sword's originality comes from the fact that it is sop stupid that nobody would use that idea. Until Cloud! Who sucks.
See sentence #1 of this post.

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Ugh, and why do you have a good quote in your signature, take it out before I vomit all over myself.