This might belong on physics.SE or astronomy.SE or not on SE at all as it's not falsifiable
I believe a meteoroid caused the dinosaurs to go extinct by causing a global winter. However Earth has been impacted by various meteoroids even in recent times.
Assume a meteoroid of similar composition to Earth. How large does it have to be in order to cause a global winter for several years? Does the flight path affect that? For example I expect in prograde orbit almost anything will simply burn.