10 Justice League Villains MORE Powerful Than Darkseid
2. The Anti-Monitor
The main villain of Crisis on Infinite Earths, the Anti-Monitor (or Mobius to his friends), is the embodiment of anti-matter and evil. His origin has been changed and amended a few times since his debut in 1985, occasionally diminishing his role as a fundamental negative force of the universe by introducing newer and bigger elemental evils (like his mother Perpetua).
Nevertheless, the impact that the Anti-Monitor had on DC continuity during COIE cannot be overstated. The series opens with entire worlds being wiped out in an anti-matter wave originated by the Anti-Monitor, resulting in the deaths of hundreds of superheroes in an instant, including Barry Allen, who wouldn't return to continuity for 23 years.
The purpose of the event in real terms was to streamline the universe by merging all continuities into one to create less confusion for new and existing readers. In that sense, the Anti-Monitor can be seen as a parallel for the dulling influence of commercialisation. Where the Monitor, an avatar of life and matter, champions creation and abundance, the Anti-Monitor wants entropy, simplicity and nothingness.