Everyone who says Arthas has a) not enough knowledge of Lore and logic thinking or b) is just a salty clown who is tired of Sylvanas.
Obviously Sylvanas would literally beat Arthas in the same way as she did with Bolvar, even if Bolvar is a bit weaker because he doesnt has Frostmourne.
Why? Its simple, because Sylvanas is not the Sylvanas we knew, she has gotten powers from the most powerful death being in the whole universe (Jailer).
Since the new retconned lore, the Lich King was nothing then a cheap copy of the Jailer, so is Arthas nothing compared to the Jailers powers.
And since I see many ppl saying that Arthas would be a lot stronger because he had much more souls... Use your brain, heres some math.
- Arthas killed millions of ppl in Azeroth, trapped souls in his Sword and got stronger
- Sylvanas doesnt need Frostmourne, because she is Froustmourne (technically she works the same way) with the exception, that you could say she has Frostmourne but 1 trillion times stronger.
Since Legion the Jailer gaines power from every dead soul in the whole fucking universe, not just azeroth. What does it mean? It means, that even if the Jailer would give Sylvanas just 10% of his new powers, she would still have like a hundred billion souls and anima more then Arthas or any other Lich King had in his fucking life.
The only and literal only chance for Arthas to hurd Sylvanas a bit, like Saurfang did, would to say the word "hope" into her face. Thats it. Then he would die the same way as Saurfang did.
There is really no room for any arguments or discussions , because it is that obvious that the new OP written Sylvanas is 10x stronger then 10 of LKs Arthas's
Infracted.