A simple poison dart, and he puts Pam in so much pain that her heart stops. In a single kill, he proves how much harm a single being can do when armed with a fortress full of doomsday weaponry.
Vulnerability to magic? Hat tries to exploit that. Superman's response is to rip the air out of his lungs to the point that he can't even breathe, much alone say his magic words.
He mocks Black with the whereabouts of Coldcast. Where is he? Headed for orbit at Mach Seven. For those unversed in such measurements, that means he's exiting Earth's atmosphere at over five thousand miles per hour. He says, quite simply, "If you had super-hearing, any second now, you'd hear the 'pop.'" Thus is the realization: if Superman wanted, he could carry most of his opponents to death.
The realization by the members of the UN that after being 'killed' by the Elite, it's not Superman anymore. He was more than just a Flying Brick: he was a set of ideals for humanity to aspire to. Stripped of those ideals, he's a morally-unrestrained demi-god that terrifies some of the most influential people on Earth with nothing more than a few sentences.
And during his confrontation with Black, he at least makes it look like he's doesn't bother with limiting collateral damage. He hits the ground like a meteor, and then effortlessly dodges most of Black's attacks to the point that his super speed looks like he can Flash Step. And then he lobotomizes Black. Even after taking the biggest hit Black could throw at him, it took almost nothing to focus his heat vision into a scalpel into a meta-gene boosted human and cut out what made him so special.
The realization that Superman created a whirlwind on the moon. It's not sci-fi artistic license: he's moving that fast.
The Atomic Skull's murder of innocent people. They're scared, they're glowing, and then crumble to dust.