Would Greta be the worst Nobel peace prize winner? Probably not, there are some strong earlier contenders:
1919 Woodrow Wilson: For handing over the US financial system to the banksters or for having the US join WW1?
1973 Henry A. Kissinger: Peace Prize for what? Negotiating the surrender of the largest military force in the world to some rice farmers? Well done, Mr. Kissinger.
1978 President Mohamed Anwar Al-Sadat (Egypt) and Prime Minister Menachem Begin (Israel): For making peace after the Yom Kippur War, a war where Al-Sadat betrayed his Syrian Ally. Why Menachem Begin is not a good fit for a Peace Prize is long story in itself, so so much: King David Hotel.
1979 Mother Teresa: Go, look up Christopher Hitchens “analysis” of this lady. Summary: she was a sadistic hypocrite.
1994 PLO Chairman Yasser Arafat, Foreign Minister Shimon Peres (Israel) and Prime Minister Yitzhak Rabin (Israel): Rabin – OK, but the other two? Too much to elaborate here, but – no.
2007 Intergovernmental Panel on Climate Change (IPCC) and Albert Arnold Gore Jr: for the hoax of the 21th century!? Also, arch-climate-hoaxer Michael Mann seems to believe that he “personally” won the Nobel Peace Prize. https://www.youtube.com/watch?v=mKbDfP5DitA
2009 Barack Obama: For not being G.W.Bush?! He should have returned the Prize after his terms, where he killed more unarmed civilians than Bush, and became the first President during who’s term the US was at war every single day. www.youtube.com/watch?v=oeDZIyGkGNM Obama: A Legacy of Ashes
2013 Organisation for the Prohibition of Chemical Weapons: For contributing to the Anti-Syria Atrocity-Propaganda. https://swprs.org/opcw-douma-was-staged
…. this list is not complete, I remember thinking there was at least one, that is even more undeserving, but the name escapes me for the moment …