What is the generally softest feeling 80+ gram iron shaft, that is still being produced?
not sure what you mean by “softest”.
You might try this link: https://www.golfworks.com/choosing-the-best-shaft-for-your-game/a/1650/
select irons. download the spreadsheet (excel), you can sort it by weight and other info that you might find appropriate to find an answer.
Maybe weakest would be a better word. Softest flex.
okay, that link should answer your question. Just a guess, but I think possibly Nippon Zelos 7 might be a choice at R2 -73 grams
Zelos 7 R2 flex in steel would be a good choice. In graphite, the Grafalloy ProLaunch 80 gram A flex might be worth looking at.