There is no definitive answer to this question as it is impossible to know for sure how much the heaviest poop ever weighed. However, there are some reports of extremely large and heavy poops that offer a glimpse into just how massive some bowel movements can be.
One such report comes from the book The Guinness World Records, which details the case of an unnamed woman who produced a poop that weighed in at 26 pounds (11.8 kg). This massive bowel movement was the result of constipation caused by medication she was taking. In order to relieve herself, she had to undergo manual removal of her stool by medical professionals.
Another record-breaking poop was reportedly produced by an 11-year-old boy in 1995. This particular bowel movement weighed an astounding 28 pounds (12.7 kg) and was also the result of constipation caused by medication. Once again, manual removal was required in order to relieve the child.
These two cases offer a glimpse into just how large and heavy some poops can be. However, it is important to note that these are isolated incidents and not representative of what most people experience when they go to the bathroom.