Despite being a founding member of the Justice League, and despite Lois' remonstrations, that he did not need to do everything on his own, that that was the entire point, of the Justice League, the plan Kal's parent's proposed to him was something he could only enact on his own.
He disagreed, that it was suicide.
He intended to live.
But he knew the others would not see it that way.
So he simply didn't tell them.
He withheld through their meeting, that deflated, defeated meeting, where none of them could offer any other recourse, except to accept Zod's offer.
If he failed, it wouldn't matter. Because he had felt that darkness. Knew that Zod was a danger to Earth, no matter what he told Kal, and the other prisoners, whose biographies he had read in horror, no matter how much he disagreed with the punishment, could not be allowed to run free, on any planet.
His responsibility extended far beyond Earth, in this case.
This was Krypton's business, after all.
And as not its last son, but one of them, it fell him to take care of this.
By any means necessary.
He would and could not allow everything his fellow Justice League members had fought for to go to waste because of his heritage, and because of his presence on their planet.
They saw him off, at the Tower. It was a sober, somber affair. Helplessness and hopelessness running rampant. Fear for the future. In the frenzy of it all, he had not had a moment alone with Bruce.
It was for the best.
He was a terrible liar, after all.
He felt rather like Orpheus. He was offered a way to bring all those he cared for out of Hades. As long as he didn't look back until they surfaced on the other side. Keep at bay all his own fears, his own helplessness and hopelessness. Remember and focus on the plan his parents' shades had given him from across the great divide.
Ever onward, and ever forward.
Hurtling into the unknown.
It wasn't the first time, after all.
Almost felt familiar.