Princess Luna could be paired with King Sombra. Luna has her own past with darkness, having once been Nightmare Moon. So she might be able to relate to Sombra in some ways. Their meetings could be about her trying to convince him to turn away from his evil ways, or they could be in a power struggle where they both have different ideas about how to rule the dark elements in Equestria.
Celestia is often paired with King Sombra. Their power levels are somewhat similar, and they represent opposite sides of good and evil, so it makes for an interesting dynamic. Twilight Sparkle is also a common character to be paired with him. Given Twilight's knowledge of magic, she could either be in a battle of wits with Sombra or trying to understand his magic for some reason.
Fluttershy might be paired with King Sombra in some fanfictions. The contrast between her gentle nature and his dark, menacing presence can create a really unique story. She could be the one to approach him and try to tame his dark side. Another character is Discord. Since Discord is also a being of chaos, his interactions with King Sombra, who is a symbol of darkness, can lead to all sorts of wild and unpredictable plots.
The best chapter pointer here is Chapter 120, "Jiang Li Can Actually Do Acupuncture?!". It opens with Facing the sudden and somewhat strange request from Jiang Li, Director Sun... and closes on Drink this." Wen Jiaojiao looked at the half cup of thick substance:....
The best chapter pointer here is Chapter 97, "Can This Really Be Broadcast?". It opens with Suddenly, Jiang Li's livestream room was packed with people, and the... and closes on And you believe what she says?.
Look to Chapter 112 for the clearest answer. It begins with These five people are supposed to be at odds., keeps building through When did they become so in sync?] [I'm dying of laughter hahaha why is..., and lands on [Hahahaha why is the Princess starting to look disappointed?] [Help, even....
If you want the clearest chapter reference, go to Chapter 100. Early on, The barrage was about to die of laughter.; later, the chapter leans on [Hahahaha, help, why is the young master always being chased!] [Next door,....
Look to Chapter 114 for the clearest answer. It begins with As time passed, the number of viewers in the live broadcast gradually..., keeps building through After a whole day of trending searches yesterday, the popularity of..., and lands on But just now, an uncle came and said not to give you.
If you want the clearest chapter reference, go to Chapter 124. Early on, Since there were too many points cards inside Jiang Li's barrel, Director...; later, the chapter leans on However, Jiang Li merely lifted her eyelids and said indifferently, "No....
The best chapter pointer here is Chapter 88, "I Call This a Test of Your Will!". It opens with She wanted to refuse, but didn't have the courage to do so. and closes on Let's go," Jiang Li said in a soft voice..
If you want the clearest chapter reference, go to Chapter 142. Early on, The ingredients for making Buddha Jumps Over the Wall were still on their...; later, the chapter leans on There were so many people in the village, just making a small portion was....
The best chapter pointer here is Chapter 101, "Hello, My Name is Zhao Daniu". It opens with Jiang Li walked over to the slope where the two had fallen down. and closes on If you encounter any trouble in the future, you can come to me..
The best chapter pointer here is Chapter 103, "Selling a Kidney to Repay Debt". It opens with Jiang Yan looked at Zhao Lang with suspicion, eyeing the dark substance in... and closes on Jiang Yan felt deep guilt welling up inside him..