It is called the Time Traveler's Paradox. In which a scientist creates a Time Machine and kills their younger self. So now a man who should not- can not- exist, somehow does. That is the Paradox, and Paradoxes are impossible.
1970
1994
2017
2013
2000
2018
1932
1927
1967
2012
2015
1979
2021
2024
2022
2019