This story starts off rather excellent. Than dxd part of the book is amazing. Then you get blindsided with a multiverse saga that is essentially just the mc going through hard time after hard time, which I think if the only way you can develop your character is through suffering than you aren’t a great writer. The powerscaling makes no sense as well, we go from losing half our limbs to muzan then going par for par with post aizen saga ichigo, with no noted strength improvements.
Other than revealing spoilers to potential readers, When he fights Ichigo he was not Ichigo's equal.
The powerscaling won't make sense if you apply that the MC is at full strength for every fight, there are characters who are faster, there are characters who are slower but might be stronger than the MC.
While my sources of reddit and vsbattle might not be 100% accurate I stick with them to keep a consistent base for those the MC fights against and scaling him on conditions, I've mentioned that in chapters before.
The MC going through hard times is what I consider the first half of the story, him growing and developing through it is natural.
If you would like to could you clarify what you mean by "with no noted strength improvements."
Have an awesome October!