In a Game of Thrones OC swordsman fanfiction, there are several contenders for the most formidable opponent. One could be the Mountain. His brute strength and combat experience would pose a great challenge. He's known for his brutality in battle and his large size gives him an advantage in close - quarters combat.
Perhaps a curved sword similar to what the Dothraki use. This type of sword allows for quick slashing attacks, which could be effective in a more fluid and mobile fighting style. The OC swordsman could have learned this style from traveling and fighting with the Dothraki or from a Dothraki - trained mentor.
I think it could be the blacksmith OC who has a strong moral code. For instance, an OC who refuses to make weapons for evil lords or sells his work only to those who he believes will use it for good. This type of character adds depth to the fanfiction and can be very appealing to readers who like complex and morally upright characters.
Another great option could be a new character, like Thoren. He was born into a family of blacksmiths, so he had easy access to different types of swords. He experimented with different blade weights and lengths, which gave him an edge in combat. He has a reputation for being able to use any sword effectively and can switch between different styles mid - fight. This adaptability makes him a formidable swordsman in the fanfiction world.
There could also be antagonists as main characters in a sense. Maybe a powerful Grimm or a rival swordsman who has a different view on swordsmanship. The interactions between these antagonists and the OC swordsman would drive the plot forward. For instance, the rival swordsman might challenge the OC to duels to prove who is the better swordsman in the RWBY universe.
One common theme is self - discovery. The oc swordsman often starts out not fully understanding their abilities or purpose, and through their adventures, they learn more about themselves. For example, in many stories, they might discover a hidden power within their swordsmanship.
One possibility could be a character named Ser Aric. He was trained by an old, reclusive master swordsman in the mountains. He combines speed and precision in his swordplay, and his unorthodox style often catches his opponents off - guard.
Sasuke would likely be a very tough opponent. He has his Sharingan and is extremely skilled in ninjutsu. His rivalry with Naruto also means he would be highly motivated in a fight.
Jon Snow - like SI OC characters are quite popular. These characters often have the same noble and brooding qualities as Jon, but with the added advantage of being self - inserts. They might use their knowledge of the original story to make different choices in battles and political situations.
One of the most memorable OCs could be a female warrior. She defies the gender norms of the 'Game of Thrones' world and is able to hold her own in battles. Her strength and determination make her stand out.
Another possible storyline is the OC swordsman's quest for a powerful sword or a lost technique. This could involve exploring ancient ruins in the RWBY world, facing various challenges and enemies along the way, and perhaps uncovering secrets about the world's past related to swordsmanship.