It could be someone like Ra's al Ghul. He is a powerful and complex villain that both Batman and The Shadow would have a hard time dealing with. His global influence and long - life plans would pose a great threat to their efforts to protect Gotham and the world.
Maybe a new supervillain created specifically for this fanfiction. This villain could have powers that combine the worst aspects of the threats that Batman and The Shadow usually face. For example, he could have the ability to manipulate shadows like The Shadow, but also be a brilliant strategist like some of Batman's foes. He might be causing a series of mysterious disappearances in Gotham, which draws the attention of both Batman and The Shadow.
The Joker could also be a main villain in this fanfiction. His chaotic and unpredictable nature would add an extra layer of difficulty for Batman and The Shadow. The Joker might see their team - up as a new and exciting challenge, and he would do everything he could to drive a wedge between them and cause as much mayhem as possible in Gotham.
Chapter 9 is the strongest chapter-level answer because it starts from Exactly, the Qiao Family isn't that great either. and follows through on Qiao, unable to save face, slapped her daughter across the face, "Didn't I....
Chapter 32 is the strongest chapter-level answer because it starts from You should know, an ID photo is like a mirror for demons. and follows through on With airflow comes water flow, and your fortune will naturally improve."....
If you want the clearest chapter reference, go to Chapter 10. Early on, Qiao's shocked face struggle to recover, Lin Manru also tasted for the...; later, the chapter leans on Jiang Li nodded with a smile, seemingly approving of Lin Manru's words and....
A practical answer is Chapter 23, because it turns the idea into a concrete scene. The chapter opens with Although Jiang Li exerted very little strength, Jiang Yan instantly felt..., adds pressure through So the moment the news broke that Jiang Li was entangling with Shang..., and ends on However.
Chapter 666, "It Really is His Mom!", is the clearest early answer because it turns Tai Fan's situation into a concrete plot event. It opens with The crowd was shocked as they turned their attention to the unknown,... and closes on Did Tai Fan just call her 'Mom' at the end?] [????.
Chapter 892, "Richard?!", is the clearest early answer because it turns Richard's situation into a concrete plot event. It opens with Zhao Lang really wanted to tell Jiang Yan the truth. and closes on Don't go!" Zhao Lang helplessly pried his hand away..
If you want the clearest chapter reference, go to Chapter 9. Early on, Exactly, the Qiao Family isn't that great either.; later, the chapter leans on They've been yelling and shouting since morning, with no sense of decorum....
Look to Chapter 37 for the clearest answer. It begins with The barrage was suddenly filled with hahas, but the two guests present..., keeps building through He Yun spent most of her time filming movies, had no interest in variety..., and lands on I look forward to your guidance." He Yun nodded.
Chapter 809, "Specially Made for You", is the clearest early answer because it turns Jiang Buchen's situation into a concrete plot event. The chapter turns that into something concrete by moving from Listening to the cries from inside the house that sounded like a pig...
Chapter 795, "Trouble Befalls the Third Lady!", is the clearest early answer because it turns Jiang Mingchuan's situation into a concrete plot event. The chapter turns that into something concrete by moving from The group photo was spreading like wildfire on Weibo.