In the future, the alien race known as the Badoon invade and take control of Earth. Michael Korvac collaborates with the Badoon and becomes a traitor to the human race. The Badoon then transform Korvac into a cyborg, and he is hurled through time by an Elder of the Universe (similar to Benicio del Toro's Collector). After encountering the first iteration of the Guardians of the Galaxy, Korvac stumbles across Galactus, where he is imbued with the Power Cosmic. Now a near-omnipotent being, Korvac was manipulated by the Collector into falling in love with his daughter, Carina (who we saw briefly in the after-credit scene of Thor: The Dark World), and is then forced into a battle with the Avengers and the Guardians of the Galaxy. Korvac is a role that could easily be brought to life by Fillion, and would potentially play a huge part in the ongoing development of Marvel's cosmic characters. The Korvac Saga is widely regarded as one of the Avengers greatest battles, and while the Guardians featured in the storyline aren't the ones we will see in the MCU, that doesn't mean the storyline can't be adapted to work with the current teams. Korvac is one of the few threats besides Thanos that would see a team-up of the Avengers and the Guardians, and could be a role Fillion might certainly be interested in.