Source: ultimatecomiccon.com

6. Omni-Man

Invincible - Image Comics

There aren't many iconic non-Marvel/DC superheroes, but Invincible certainly qualifies.

The landmark series just recently wrapped up after close to a 200-issue run. But it all started with a simple concept: What if your dad were the greatest hero on Earth? And what if you began to inherit his powers?

Mark Grayson always looked up to his dad, but was his dad worthy? As it turned out, no. Nolan Grayson, aka Omni-Man, wasn't a champion of the downtrodden, a defender of the weak; he was a galactic conqueror prepping the Earth for conquest under the Viltrumite Empire.

He put his plan into action by massacring the Guardians of the Globe and asking Mark to join him as fellow conqueror of Earth. Mark freaked out and fought back. Omni-Man responded by beating his own son almost to death, fracturing his bones and atomizing his blood vessels. Yeesh.

Omni-Man would have a much longer and more fully developed character arc throughout the rest of the series, but that first set of arcs really made quite a first impression.