Hello, I can't quite say for certain, but my guess is that this could be a raccoon latrine site (i.e., a place where a raccoon repeatedly returns to defecate. You could put a trail camera at the location to see if one returns.

Note, if this is raccoon scat, use caution if removing the scat as raccoon scat can harbor a dangerous parasite (Baylisascaris procyonis).

https://naturetracking.com/raccoon-vs-otter-scat/

Best,

That is much larger than I thought it was from the original picture. I'm still not sure what else it could be other than raccoon. It's a really odd place for any other animal to defecate. Sometimes old decaying fungus/mushrooms can almost look like animal poop and can smell quite rotten as well, but you can usually still make out some characteristics of the mushroom. If it is a raccoon latrine, the scat may appear larger because multiple scats have piled up together. Raccoon scat can be highly variable because they eat such a wide range of foods. If they're eating more animal matter, it could explain why it smells so bad. Sorry I can't give a more firm answer, I might put a trail camera up if you're really curious what might be doing this.