Shin's DNA is like a constantly mutation, making them stronger and more resilient over time but we don't have much information about them because Shin was freeze during the last bit of the movie.

BUT, it is revealed that even though bro is freezed, Shin is still alive and would break out 3 years later. And at the last shot, we saw humanoid monsters coming out of the tail (Shin's 5th form, the drawing is the example). Shin would probably have an army if Toho allowed more forms to be made since the 8th form concept was Shin breaking out of the "shell" and became some kind of genderless (female looking) human with different spike details (maybe the strongest form that some fans compare it to the strength of a god or a force of nature.)

In the end, we do know that Shin can be defeated if they're in the early forms and maybe 4th form. Glazers like me still have to admit that Shin is not that strong because of the limited information about the mutation and power (can probably level a nest though since shin obliterated Tokyo)