Easily one of the most liked characters from Demon Slayer is Nezuko. You can't help but feel for her more and more as the series goes on. The way her powers develop as the series goes on is well done, slowly letting her work her way up until she ends up as one of the more powerful characters by the end.
While that holds true in the Demon Slayer universe, would it translate to the Forgotten Realms? Would she still be one of the top tiers or fall to the mid? There's certainly plenty she could steamroll her way through, pushing past them like they were kids on a playground. There are more than a few that could put up not only a fight but outright beat her.
10 Destroy: Acolyte
Acolytes are the types of characters a level one adventurer would be, the young who are hoping to be a full-fledged priest in their clergy. As you'd expect, they lack the skills you'd want in both combat or life as a whole, very much like a teenager transitioning into adulthood. As such, what chance could they have against a demon-like Nezuko? She could probably tear an entire clergy apart if she were evil. A group of acolytes would be like younglings being cut down by Anakin's lightsaber.
9 Put Up Fight: Black Dragon
It's a dragon, what more need to be said? Even the strongest of characters are going to struggle when dealing with a creature that could lay siege to entire cities. Color of the dragon doesn't much matter either, as they are all formidable opponents in their own right, types of breath being all that really changes with them. With a black dragon, you have to deal with its acidic breath, and it's sheer frightful presence, causing fear to strike many that stand before it.
8 Destroy: Animated Armor
Animated armor has a nice role in D&D campaigns, giving you the ability to pull a surprise on your party without having the risk of it wiping them as a mimic would. Their strength is all in their false appearance, lulling people into a false sense of security before it strikes.
The one issue with that is unless it found a way to end Nezuko in one strike, she'd punch a hole straight through the armor. Her strength levels are far too high for a creature like this to be more than a training dummy.
7 Put Up Fight: Androsphinx
Androsphinx's may look like they regularly visit a hair dressed, but they are far more than just a luxurious mane. They are extremely difficult creatures to deal with due to just how many types of healing abilities they have. They have three different spells that allow it to recoup it's lost health. That naturally means it isn't attacking, but it can wear you down due to this. It can be disheartening to see a creature withstand so many of your attacks and still be standing. That would be a difficulty even Nezuko would deal with.
6 Destroy: Assassin
Assassin's can be some of the most dangerous mid-tier foes you can face in a game. They can dish out a boatload of damage upon their first attack, so long as they get the drop on someone. Between assassinate and their sneak attack, even some of the staunchest fighters could be put into immediate danger. The issue when it comes to Nezuko is it wouldn't be enough. Her ability to regenerate is far too high, allowing her to weather the opening salvo with ease. From there it would just be about her landing a single blow.
5 Put Up Fight: Balor
Balor's are mammoth-like creatures, standing at over 12 feet tall and easily over four thousand pounds. They are creatures born of war, generals who constantly serve as pillars to their race. There's a good reason for that too, their fighting prowess is downright frightening.
From the fire damage that's attached to the flame whip to the sheer fact, they triple their damage dice on longsword hits rather than just double. The scariest part may the fact that they explode upon death, dealing 70 damage to those near them. Even if Nezuko were to win, she'd have to survive that as well.
4 Destroy: Bandit
Bandits are your typical ruffians, the types of men and women who think they are way tougher than they are. They prey on the weak, to boost their confidence. When in reality, they would stand very little chance against a real fighter. That would be the case here as it would take ten or more for Nezuko to even break a sweat. Nothing in their arsenals would be of any concern to her, and it feels like they'd even be lucky to land a single blow on her.
3 Put Up Fight: Behir
You can just look at that image and know that you're in for a tough boss fight. That glare in its eyes is something only a creature with thoughts of devouring you whole would have. This is apt considering it's one of the few beasts that can do just that, eat you alive. Once swallowed, you get dealt with damage from its stomach acid until the rest of your party does enough damage to get it to regurgitate you up. It's all a messy business made even worse by the fact it also has lightning breath. Even someone as strong as Nezuko would struggle.
2 Destroy: Death Dog
While the dog may look more than a little intimidating, its two heads looking like they are going to fight each other over who gets to take a bite out of you first, it's still just a dog. There's only so much an animal can do against a normal adventurer, let alone someone strong enough to cleave one of those heads clean off. The only chance the beast would have is to catch Nezuko while she was sleeping and even then, with her regen, it wouldn't even be enough.
1 Put up Fight: Deva
When talking about a demon-like Nezuko, what better foe to put in her way than a celestial? Devas, as you can see from the image, are a type of angel, one that's a mix of a healer and a warrior. What makes them so dangerous to Nezuko isn't that, its the radiant damage that's attached to their mace. Each swing is embued with radiance, adding 4d8 to any successful attack. Those numbers can add up over time. The battle would go back and forth with even the victor feeling worse for wear by the end.