How to reduce pepper in soup?

You can try adding a few potatoes pealed and chopped in large chunks let them cook and soak up the seasoning then discard them. This method works well for salvaging an over salted soup but it should at least help a little with your pepper predicament.

There isn't much you can do, but my method would be to create another 1/2 batch or 50% more of the soup without seasoning. Add to what you already have and the pepper flavor will be weakened.