Here is the full list of all 18 Red Line achievements.
Prologue Completed
ChapterⅠCompleted
Chapter Ⅱ Completed
Chapter Ⅲ Completed
Chapter Ⅳ Completed
Chapter Ⅴ Completed
Epilogue Completed
The story has a bad ending.
The story has an average ending.
The story has a happy ending.
Investigate all flush toilets
Talk to all pedestrians in Sun Xuelei's storyline
Complete all clues in the average ending
Talk to the policeman by the roadside
Not to get caught by the grandma
Not to get caught by the malice
Not to get caught by the mind flayer
Bid farewell to everyone