Making 120 different alchemy items sounds incredibly tedious.
Is it as annoying as it sounds? :<
To be honest yeah it can get annoying at times. When I first started going for the trophy though I was surprised how many recipes I could make. I barely used alchemy until I had to for this trophy it was my 2nd to last one. Though once I got to the last 5 recipes it got tougher because the items were either relatively rare or I just needed so many of them to make some e.g bubble pipes.
Another note if you do go for it ignore the recipes for the kaledo stones and the scrolls of truth because that would take way too much time.
Got it yesterday at ~78 hours. I left the Guardian Trophy for last because I like to finish the plat with a trophy like that rather than a grind trophy. Of course that guy was fodder for my team at that point, I was disappointed.