Her appearance is one factor. Maybe she has a pale face, or strange eyes that seem to look right through people. Also, her behavior like not blinking or staring constantly at passengers is really creepy.
Well, it's a combination of things. Her unearthly silence for starters. She doesn't interact like a normal person. Then there are the strange occurrences that seem to happen around her, like the lights flickering. It gives the impression that she has some sort of otherworldly power or is associated with something supernatural, which is quite frightening.
The fact that she is so out of place on the train. She doesn't seem to belong there, yet she is there among the normal passengers. Her actions, like whispering things that no one can understand and disappearing suddenly, all contribute to making her extremely frightening. It's like she represents the unknown and the things that go bump in the night, and that scares people on the train.
Chapter 83 is the strongest chapter-level answer because it starts from When they received the task, the three of them were already sharpening... and follows through on Since all the guests were staying at Uncle Zhao's cabin, Director Sun....
Look to Chapter 91 for the clearest answer. It begins with When Jiang Li saw that he had been assigned a harrow, Qi Tianyu felt his..., keeps building through My tool couldn't possibly be a shovel, could it?" Director Sun chuckled..., and lands on Hahaha, Young Master, what the heck are you.
Look to Chapter 108 for the clearest answer. It begins with In a glamorous Michelin three-star restaurant, Su Yinwan and Shang..., keeps building through The elegantly dressed waiters started streaming in, serving them various..., and lands on Hey, I've been waiting for you for so long, where have.
The best chapter pointer here is Chapter 73, "Does Someone Like Jiang Li Deserve to Have a Fan Club?". It opens with Director Sun, tongue-tied, finally managed to squeeze out a sentence,... and closes on Despite Wen Jiaojiao's fiery temper, there were still many who were drawn....
Look to Chapter 125 for the clearest answer. It begins with Next, it was Qi Tianyu's turn., keeps building through Although he didn't know what Jiang Li had chosen, just from her recent..., and lands on He deliberately chose the most inconspicuous wheat seeds..
A practical answer is Chapter 116, because it turns the idea into a concrete scene. The chapter opens with But before the audience in the live room had time to continue brewing the..., adds pressure through So, he quickly nodded as if pounding garlic, "That would trouble Sister Li..., and ends on.
The best chapter pointer here is Chapter 116, "Group Freeloading!". It opens with But before the audience in the live room had time to continue brewing the... and closes on Their old Jiang family never had such twisted genes in hundreds of years!.
If you want the clearest chapter reference, go to Chapter 72. Early on, Jiang Yan was still griping when suddenly a fair hand reached out beside...; later, the chapter leans on I'll take these, thank you." In an instant, five pairs of eyes stared over....
Chapter 69 is the strongest chapter-level answer because it starts from Since the phones issued by the program team couldn't log into Weibo, Wen... and follows through on Wen Jiaojiao immediately hugged her arms proudly, specifically waiting to....
Chapter 113 is the strongest chapter-level answer because it starts from The next day, Jiang Lili was up before dawn as usual. and follows through on If things are really as you say, that is indeed quite serious..