Had Planet X been a little bit larger there would be an asteroid field where Earth is today. Had Planet X been a little bit smaller or hit at a different angle the Moon would not have formed or multiple, smaller moons would have formed. If the moon had been larger it would have caused massive, constant earthquakes and severe tidal patterns.

Thanks to the Moon the oceans have strong tides (but not too strong) and the air has weather patterns. The Moon’s gravity sucks up quite a bit of the cosmic crap that otherwise would crash into the Earth and wipe out any life evolving. W/O the Moon life as we know it would not be possible. Figure out the odds of a planet in the water zone around a star being hit just right to form the Moon and and you’ve found your Great Filter.