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After many tries and fails, I decided to write here.
On Steam, if you go to any badge page (eg: Badge) for each card you miss, it shows all friends that have that card
I am trying to change their name to the nickname I set for them (if any).
I couldn't find any Steam API that gives you nicknames.
You can find the nickname on the page directly only if you mouse over their avatar, but if I do it this way, it takes too long to load.