I'm guessing that many will already die in the war. And well, the strongest fear nothing, even Tang Yichen alone is capable of holding all the other Shangtians in check (not saying he's capable of killing them all at once, far from it).
It's just my assumption, in normal novels after each major breakthrough the cultivator suffers an exponential increase in strength, if Nicky follows the same logic, the MC at the beginning of Qi Sea will be much more powerful than an EX or MX, with the difference being even greater when he reaches Core Formation. In this case, it's quite plausible that the MC at the moment of stepping into Core Formation will already be more powerful than someone like Tang Jia or even Yang Bohai.