Just to clear one thing, the spoiler provider doesn't say who is the one that Kaidou attacks
마지막에 카이도가 모모노스케 있는 곳에 등장해서 바로 ○에게 쇠방망이를 휘두름.
Based on papago mtl: At the end, Kaido appears where Momonosuke is and immediately swings his iron bat at ○.
The ○ is a word used to censure the name in order to not say who was it, it's like the 'xxxxx' to us. ○ is also used in japanese to not say the word. At least i'm guessing that's what he's saying since the next sentence after that he says this:
○은 몇 분 단위인지, 혹은 글자수로 누구인지 특정하지 못하게 가리는 역할임.
But since i don't know korean at all and i'm just saying what i think based on MTL's I can't confirm anything. Someone who knows korean should specify this.