The Last Man on Earth was (or, depending on the point of view, will be) a male dognose in a possible future timeline of the Prime Universe.
In one possible timeline of Earth, this banker-warlord took part in the Great Wealth Wars of the distant future for total domination of all the riches on the planet. The war and all the chemical weapons used in it proved to be the doom of mankind and their planet, however; the last survivor (though dying himself), this man, in one last moment of lucidity, recorded a video message explaining the circumstances of humanity's fall to possible alien visitors before dying himself. Time-traveling Scrooge McDuck, Donald Duck and Gyro Gearloose viewed the message shortly before witnessing Earth's final destruction in a collision with the Moon.
Behind the scenes
The Last Man on Earth can be seen in the 1973 story Money is the Root of Upheaval.
In the 2018 localization by Joe Torcivia, to avoid potential censorship, he states that he will attempt to flee the planet before its destruction, instead of bleakly accepting his impending death.