In the same encounter, the fact that the Legion are here to see their friend one last time.
Cosmic Boy: Goodbye, Superman. We...we always miss you.
Lois: "He never told me exactly what happened that night before the siege began, but as soon as I saw him the next morning, I knew something had upset him. He looked funny. He looked as if he'd been crying."
Lana Lang, after hearing from Superman's own lips (thanks to newly-gained super hearing) that he loves Lois and not her, flies off with Jimmy Olsen to their deaths in an attempt to end the villains' attack on his fortress.
Lana: We're only second-stringers, Jimmy, but we'll show 'em. Nobody loved him better than us. Nobody!
Superman screaming, "YOU HURT LANA?" was also a Gut Punch.
The Justice League tried to get into Brainiac's shield, but despite their desperate pounding, this battle the Man of Steel would have to fight alone. Think of how sad that would be: The Paragon you always looked up to is in trouble, and all you can do is watch helplessly as his enemies come at him one by one.
Vartox, who was, in pre-Crisis chronology, engaged in a romantic relationship with Lana Lang, cradling her lifeless body in his arms, bawling like a baby. The man who is too powerful for Superman to contend with. This is a character whose earliest two appearances involved the loss of first his wife, and then his homeworld. When the first Crisis wiped out his existence, this poor bastard was probably grateful. . .
For what little it's worth, he's alive in the post-Crisis DC 'verse, and much, much happier on the whole.
"...And by the time I realised where he was heading, it was too late. As he walked into the blinding golden light he turned and looked back over his shoulder. He smiled at me...I never saw Superman again."
Even the death of Luthor, as he begs Lana to just end it for him.