The article below has a lot of good information.
Safest countries in South America to visit: 6 places to travel stress-free
I’ve personally traveled to all of the countries (and most of the sites/cities listed as well) and generally agree with their assessment.
With that said, I would exercise caution in two places mentioned. The first is Buenos Aires, Argentina. It’s a big city in a country suffering an economic collapse. While most areas are probably OK, I’m hesitant to give the entire city a “safe” rating.
The second is Ciudad del Este in Paraguay. On the border of three countries, this city has a lot of drug trafficking, human trafficking, and stolen goods. Be exceptionally careful here.