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.
1943
2014
2017
2013
1947
2015
1948
1946
2023
1993
2016
2024
2019
1928
2003