Well, it depends. Some spoilers could come from insiders with real information, but others could just be made up to generate buzz. You have to take them with a grain of salt.
Webtoon does have a few 18+ comics. However, their availability can vary depending on your region and the platform's content regulations. Some might be hidden behind age verification or specific access settings.
Well, spoilers in light novels related to gamers can be really annoying. For example, if you're into a game - based light novel series and someone reveals a major plot twist about a character's in - game power - up or a crucial event in the game world that the characters are part of. It can ruin the excitement of discovery when you finally get to that part of the novel.
Well, there are some major plot turns in 'A Will Eternal' that you wouldn't expect. However, I suggest you discover them yourself while reading to fully enjoy the story.