This person are giving false -REP and has been stalking me on other platforms and accusing me of things I didn't do.
Judging by his words, someone with the same avatar as mine cheated him for 2 TF keys, but even according to his screenshots, he has a completely different nickname than mine.
I explained to him how to check the steam chat history to see the user's Steam ID and make sure I didn't actually have any dealings with him. I also explained to him about this type of fraud - as a impersonating and gives him link to guide how to not be scammed.
But he continues to threaten me and wasting my time.
Be careful with this guy!
Not recommending to trade with him until he learn steam interface and how to protect themself about basic scams.