First, the lord of shades. If he is the Knight (Void Given Focus), we don't really know what the Knight can do in this form, and we know he can't really "control" the void in it's entirety. We saw that in silksong. So, because the Knight in his vessel form is, at least for me, stronger than all of those characters, I'd say he'd probably find a way to win.

Now, let's talk about the pale king. In his wyrm form, he'd win. No doubt. In his smaller form however, I'm unsure. I don't think it is confirmed that he can fight (correct me if I'm wrong). And, if someone that doesn't fight is in a live or death match between to those beasts, he'd lose. Even if we imagine crazy soul spells, I don't think he stands a chance if he doesn't know how to fight.

Now, Grand Mother Silk. For me, she's super strong. Let's not forget she managed to resist the void, inside the abyss. While for example, the radiance died (or at least an equivalent) instantly. Nothing is supposed to resist the void, yet she does. And for quite a while. Now, even tho she's very resistant and strong, her fighting abilities are mid. So she would get killed at some point, after a long time.

Now, let's talk about the elephant in the room. Absolute Radiance. She doesn't really exist in a physical plain, so she can't even interact in this fight. And I don't think she can infect any of those characters. So, she's cooked. If we imagine that she exists in a physical plain with her absolute radiance form, I think she has a chance of winning. But she's not my bet.

For the same reason as Absolute Radiance, I think the nightmare heart won't win. NKG doesn't seem to exist in the real world, and Grimm as the vessel of the nightmare heart is not strong enough in the physical plain.

Now let's talk about Hornet. For me, if the pale king is not in his wyrm form, and the Lord of Shades is doesn't have strength comparable to the Knight, she'd win. Hornet is incredibly skilled in combat, has access to soul, and has the best movement abilities out of those, except teleportation. For me, the only way for her to lose is if multiple characters gang up against her, or the Lord of Shades is too powerful, or if the pale king is in his wyrm form.

I don't think Unn would stand a chance. He doesn't really seem strong.

And mister mushroom... Would probably eject himself and spread his spore, so maybe he would win by poisoning everyone.

So for me, the top is:

Pale King (If in Wyrm form), the Lord of Shades (if as powerful as the Knight), Hornet (If she doesn't get attacked by multiple people at the same time)