Who is the best blade master lore wise

he has a blade.

You said bladesmaster.

Therefore all champs would have a sword.

Therefore Jax wouldn't be held back by a lampost.

Jax stomps.

I'd go with Jax, Grandmaster at Arms.

Either Jax or Yi.

It's hard to tell, most likely either Yasuo or Master Yi.

Khada Jhin before the Ionia/Noxus War. The guy managed to evade wuju highwaymen (and was probably able to out-duel / kill them) for goodness sake. It also took 3 people to take Jhin in and I doubt it was easy. He made his art with blades. Can you imagine what grotesque carvings he made out of his victims? Or how he probably managed to slice them to ribbons and still, in his eyes, make a masterpiece out of them?

So, let's see: Irelia has a spiritual connection to her blades. She isn't technically proficient with a normal sword, well, at least not extraordinary. Yasuo uses a special technique, his sword his somewhat special and he relies more on being fast than forceful. Fiora focuses on precise attacks, while dodging and punishing the enemy. Yi. Well, Yi is fast too. He also relies more on hitting an enemy often, rather than hard.

Then we have Jax. Jax is fast, hits hard and often. He can dodge almost any attack and all his lore tells us is that he is unbeatable in combat. I'm pretty sure Jax would lose to, let's say Aurelion Sol, but he can probably beat almost any human who uses physical attacks and a few more.

Lore wise? That would be a non-champ, General Du Couteau. The dudes skills with a knife are supposedly inhuman.

"Imagine if I had a real weapon!" -Jax

He would take them on 1 vs 3 and come out on top! Sure Fiora have some sick skills, Yasuo can control the wind, Irealia have telekinesis and Master Yi is a master of wuju but Jax is even with one of them when he uses a small lamppost. He would totally kill them all with a sword!