Hi, welcome to Superpower Wiki! Thanks for your edit to the File:God Blade.png page!
Since I don't know a thing about the series, I'll have to go by your description and that sounds more like Fate Denial/Fate Immunity, possibly Freedom. And if that part of controlling fate is literal, Destiny Manipulation. --Kuopiofi (talk) 05:28, January 5, 2019 (UTC)
There aren't any demonstrated feats for Nangou or Ryouma to support them.
Ikki can't match Edelweiss in swordsmanship and Ouma's powers are related more about his muscles rather then true mastery of the blade (and even then he is on the same level as Ikki, which means Edelweiss would still surpass him in skill)
Edelweiss alone is the only one who belongs on the page and has actually demonstrated proof of her skill.
Edelweiss has beaten every combatant that has been sent after her, so much so that they don't do it anymore.
Ikki even confirms that Edelweiss's skill with the blade surpasses his own.
Edelweiss has been the only user of Supernatural Swordsmanship since the story began. Ryouma never shows any feats (and all accounts of his skill are secondhand mentions, rather then actual on screen/on panel feats).
Zoro was personally trained by Mihawk, and his skills have continued to improve to the point that he is essentially on the same level.
Oden's skill is such that he could stand equal to Kaido (also doing the impossible by wounding Kaido, which has never been topped since), Whitebeard and Roger (something that not even Mihawk could ever hope to accomplish)
Ryuma is the only swordmaster in the series to have his own legend and personal series.