Omni-Man's Thousand-Yard Stare after murdering the Guardians. Is he simply exhausted from the fight, or is he overcome with guilt as the adrenaline wears off and it really dawns on him what he just did? The fact that he suffers from an increasingly severe case of Conflicting Loyalty afterwards only serves to muddy things further.
Some theorize Omni-Man let the Guardians beat him up so he would have a legit excuse for being the sole survivor of the battle. To add to this, was Omni-Man struggling against the recently resurrected Immortal a sign that he genuinely was struggling against the combined might of the Guardians, or was it simply the result of Omni-Man being both distracted and tired out from his fight with Hail Mary?note To split the difference, it's entirely possible that Nolan intended to let the Guardians rough him up a little But he underestimated just how powerful his teammates were - and by the time he decided to get serious he was already wounded and genuinely struggling.
During his fight with Mark, just how much of Omni-Man's ranting was directed at his son and how much was directed at himself. It all depends on which one and when the viewer thinks he's trying to justify his actions to in the situation.
Even Mark invokes one at his father: if Mark had never developed his powers, would Nolan be talking with the Condescending Compassion about how they're going to outlive everyone so they are better than the humans on earth? He asks if his mother's life means so little to his father and if Mark would have not mattered at all. Omni-Man asserts that Debbie is just a pet, and he would have seen Mark the same way, but his tone wavers, and Debbie despite herself can't believe it.
Nolan openly tells Debbie that he wasn't prepared for Mark to get his powers since he was a later bloomer by Vitrumite standards, and that their lives might have been better if he had never gotten those powers at all. Does this mean Nolan would have given up his Viltrumite ways and not slaughtered the Guardians if Mark hadn't developed powers? Or is he simply covering for his rather sudden outburst at his wife?
Considering the revelation that Robot is actually a human named Rudolph, was the selection of the new Guardians of the Globe just so happening to include Eve, Rex, and Kate coincidence? Or did his bias make him choose them as a result of working with them for three years prior?
"You, Dad. I'll still have you." Was Omni-Man's apparent regret at his actions because he realized he was destroying one of the only people alive who loved him unconditionally, even after a no-holds-barred beatdown to near death? Or did he realize that, without Mark, there would be nobody else on the planet to share his eternity with, and he'd be left to the same horrible fate of loneliness he had described minutes before?
Is Cecil that different from Omni-Man? While he doesn't want to kill Nolan until it's absolutely necessary (although Nolan himself also seems to have held back on his own mission until Mark developing powers seemed to push up the schedule), and tries to reason with him while buying time for the GDA to contact Mark and warn him about his father, saying that Omni-Man was his friend and not a senseless killer. He is much less extreme and his reasons for his actions are that he wants to protect the Earth and its civilians, and is shown to give free healthcare to badly injured heroes, as well as helping with the practicalities of rebuilding houses, and lives. Yet like Omni-Man, some of his more heinous actions like sending his own men into situations he knows will get them killed within moments are not at all prevented by that compassion and his motivation with it is also atrocities for the sake of his planet. Both men also very much want Mark to turn out a very specific way for the sake of their planet, regardless of what the teenager himself wants.
Some fans wonder whether or not Amber was telling the truth about knowing Mark was Invincible or lying to try to maintain face.
Omni-Man not choosing to help Mark and the others against Battle Beast. Was it simply a cruel way of teaching Mark a lesson, or, considering how powerful Battle Beast really is in the comics, did he know that he couldn't win even if he did intervene?
Some people theorize that the reason the mind control device didn't work on the Immortal wasn't because Robot gave the Mauler Twins bad schematics, but instead because he was so mad at Omni-Man for killing him and the Guardians of the Globe that he broke out of the mind control using The Power of Hate.
Mark losing himself to his anger to kill Angstrom Levy in the season 2 finale, he claims, "I thought you were stronger". Saying those lines in a literal sense, Mark could have been commenting on his expectations that Angstrom Levy had enough Super-Toughness to endure his punches. On the other hand, Mark's line could have been to himself for failing to live up to his own principles as a hero never giving into his worst impulses.
When the Immortal explains to Cecil how he could have caused an interplanetary war with Allen, did he genuinely believe his claim to be the "King of Space" or did he not but just assumed that hurting or killing Allen would have caused a conflict.
