In weighing the damage caused under Carter's watch and since, limiting him to the worst president in the last 100 years is beyond generous. His complicity with tyrants and terror has created much of the terrorist threat that the world faces today and has empowered terrorist to bring their terror to almost every continent. He has meddled in foreign policy attempting to undermine the US Government and other foreign powers. I would say that Carter is the worst leader since Homo Erectus and I am not sure he is one of them; ie. possibly a lower order reptile.
Stabbing reported in Kiryat Gat in southern Israel (Haaretz)