Both Pluto and Charon have a dearth of craters made by small objects.
What did the earliest bodies in our Solar System look like, and what was their fate? It’s difficult to tell, because it’s not clear that there are any of them left. Lots of the earliest material was swept up into the planets. Many of the smaller bodies that remained are products of multiple collisions and have perhaps formed and re-formed multiple times—some are little more than rubble piles barely held together by gravity.
Source: Craters on Pluto suggest Kuiper Belt ate its smaller bodies | Ars Technica