Don't kill the one story. Expand until it is two:

Slightly contradictory, but consider if your story is too long. Does it keep focus throughout the work? Are all areas of those pages equally relevant and fleshed out?

I was in a similar situation to you, and the advice I got was "Couldn't this be a whole series?" It made me realize that the first half was actually kind of light on details and plot development. I realized that if I cleaned up the first half, and gave it the kind of quality and meaning it deserved, that my novel would be absurdly huge. So I broke it into two stories, adding the details to give the first half a resolution. I didn't need to cut - quite the opposite, I had to add scenes and content to make the first half fully functional as a standalone work.

But in the end, I was much more satisfied telling the full story I wanted in two parts than trying to cut the original down to fit a preconceived idea of what a first story should be.

• PS The fantasy/sci-fi field tolerates longer stories, but I was told that the FIRST novel by an unknown author is better short because there is less cost/risk in getting a shorter work published by an unknown author. I can't verify if that is true, but it makes sense.