User blog:Mgf60/Profanity in Vol.3 Chapter 119

In Korean media swear words are usually covered up by replacing one of the hangul with an "X" instead, which is also how it is done in Tower of God.

The sentence with the swear word is "x발 새끼.", which is the censored sentence of "씨발 새끼." "씨발" is translated to "fuck" and is used in a similar way, since both "씨발" and "fuck" are sexual in nature, but it can also be translated to bastard/bitch or similar. Meanwhile, "새끼" means cub/young and can be used as an insult in itself or the name of a young animal, but when combined with the name of an animal or a more traditional swear word like "씨발" the meaning is made more clear.

Lo Po Bia Yasratcha calling someone like Lo Po Bia Traumerei, who is much older and of higher rank, a cub is likely meant to say that Traumerei is like a child (immature). This would give the translation of "Immature fuck", but the Line translation of "son of a bitch" is also valid, with the meaning extrapolated being "Bitch's cub"