This achievement seems to be bugged to a lot of people, including me in a few minutes ago, but now I believe that is hard to know what is the trigger of it. For me, it took a lot of tries to work, and here goes my entire experience:
*Start a expansion pack in a save just after ending the main story of the game, and all activities in the map Velen/Novigrad made.
*At first, go to the notice board at the Seven Cats and then at the Brunwich. Then talk with a Shopkeeper at Upper Mill, at the conversation, do the mission "Races: Swift as the Western Winds" and started "From Ofier's Distant Shores". Do this mission perfectly, killing and looting every fallen knights and their campsites at the way.
*Never sell or use any item that you looted, when you get heavy, use an ability called "Strong Back" that allows you to carry more 60.
*At "From Ofier's Distant Shores", do the mission until is showing "return the diagrams to the Ofieri merchant", and do not conclude it.
*Then start "Evil's Soft First Touches" mission, this is just the trigger to get other mission, called "Rose on a Red Field", and do it at the same way you do "From Ofier's Distant Shores", killing and looting every fallen knights and their campsites, without sell or use any item that you got.
*"Rose on a Red Field" must be made until is showing "go to the woman who hired you to collect your reward". Do not conclude this mission too. (At this point, I did the same with a mission called "Without a Trace" until is showing "report back to the herbalist", but now I don´t think is needed).
*Just then, you should go to the other campsites showed by a Foxfire49's solution, always killing and looting every fallen knights. DO NOT SELL OR USE ANY ITEM, carry everything. Maybe concluding missions that you could miss some item. There´s no problem to die or use a Fast travel point. And I do not use any item, but read everything. I made all on Death March difficulty, but I don't think that is necessary.
Thanks to @Foxfire49,
Enjoy, and good luck.