Question: I can think of a number of potential Titan Avatars to confront the Chinese pantheon, but none of them possess the same importance as either Apep or Kronos. Do you have any thoughts about this topic that you could share?
Oh, China. What are we going to do with you?
You're right. There really isn't a single Titan Avatar you can hold up in China as an example of the same kind of giant, overarching antagonist that you have with an Apep, Surtr or Kronos. This is mostly because China's mythology is a massive conglomerate of different religions fused together over a huge amount of time; unlike the Egyptians, who believed in basically the same gods (albeit with evolution and syncretization) over the lifetime of their religion, the Chinese have three or four different sets of them that have been smashed together into one zany whole, and their myths and legends are likewise tangled and inconsistent. No one Titan has taken on the Bureaucracy the way Surtr takes on the Aesir, and that's because no one Titan is universally involved in all the shenanigans of the multi-faceted Shen. Everybody in the Greco-Roman mythos understands that Kronos/Saturn fought a losing war against the gods and was imprisoned as punishment, but China might say that about different figures all over the place, none of which are necessarily universal.
Basically, China has too much going on for a single antagonist to cover it all. No one bad guy is going to be a big deal in all the many religions that together make up the synthesized Chinese mythology. There is too much China to love.
That doesn't mean that China doesn't have Titans, because it definitely does, but rather that they tend to appear with more variation in power and importance than those of other religions. China also has more than its share of the kind of Titans that aren't necessarily overtly antagonistic - beings like the gigantic, primordial Pangu, who is certainly not antagonist toward anyone but also fulfills a similar creation-Titan role as beings like Ymir or Tiamat, or Shang Di, the power of Heaven who was worshipped almost monotheistically in the most ancient Chinese religion and who bears a striking resemblance to Aten in some ways, but who also is still held in the highest regard as a distant, only seldomly-personified concept. These guys are almost certainly Titans, being way too ancient, uninvolved and gigantic to be really comparable to the gods with whom humanity has close ties and relationships, but they're also not exactly breaking down the Overworld's door.
Obviously, don't quote me on this as OFFICIAL JSR LAW or anything, because we are far away from being able to do a rewrite of the Celestial Bureaucracy (we're still knee-deep in the Orisha and it looks like you guys are heavily favoring the Amatsukami for the next pantheon project), but if I were to try to choose the best directly antagonistic Chinese Titan to oppose the Shen, it would probably be Gong Gong. A massive watery dragon (occasionally also described in human form) with a distinctly bad attitude who represents the capricious destruction of natural disasters, he basically rebelled against the Jade Emperor and the Bureaucracy in protest that his massive powers were being restricted by the regimented order of the Chinese pantheon, and along with hideous demon minions decimated much of mythical ancient China's population while running rampant in his campaign to overthrow the gods. He didn't succeed (when do they ever?), eventually being defeated in a many-day-long battle across the heavens with the ancient fire god Zhu Rong, a tiger-riding, sword-wielding badass, who threw him back out of heaven to the earth. Gong Gong proceeded to smash his head into the ancient mountain Buzhou, one of the pillars that supports the heavens, causing it to collapse and unleashing various other natural calamities, including tearing a hole in the sky that disrupted the course of the sun, moon and stars, causing huge rivers of lava to run out of the destroyed pillar to burninate everything nearby, and flooding pretty much everywhere else. It was at this point that the goddess Nuwa famously leapt into action to repair the hole in the heavens and add new supports to keep the Overworld from falling down, but even she could only do a patch job, and as a result the heavens have a permanent northwest tilt thanks to the uneven pillars. (And that tilt, and the accompanying disorder of the world, is the reason all rivers in China flow southeast - the more you know!)
So, yeah, that guy. He's a relic of older mythology and doesn't have a lot to do with later Shenism and Taoist philosophy, but he's my best bet for a Titan who directly opposes the Celestial Bureaucracy and is enough of a serious, dangerous threat that the whole pantheon needs to mobilize to deal with him. His release with the sundering of Tartarus would almost certainly be bad news for the Shen, and they'd have the same problems with him they did before - he moves quickly, they move slowly, and while he's loose he's pretty much blowing up everything all over the map.
There are, of course, other candidates for Chinese Titanhood besides Gong Gong, so don't feel like you have to run with my suggestion if you have another you like better. Since there's so much of Chinese mythology to go around, it only seems right that we all enjoy whatever crazy bits of it are most appealing!