Out of all the scenes in Smallville with Lois and Clark, this scene pretty much says everything about their relationship and it’s beautiful beyond words. In this episode, Lois time travels into a post-apocalyptic future where she meets a powerless Clark who has tried everything he can to take down Zod and his army of Kandorians, and during the whole episode they pretty much expose their souls to one another as they might not make it out of this alive.
So after Zod’s solar tower has been shut down, the sun returns back to its original state and it looks like the tables have been turned…Until Zod stabs Clark with a kryptonite dagger, leaving him to die. After such a brutal fight as a powerless man and having normal sunlight back for only a brief time, Clark’s healing factor hasn’t yet come back yet, so he uses his remaining time for Lois and makes her escape back to the present his main priority.
As for Lois, she doesn’t want to leave him while he’s mortally wounded with no backup, and she’s scared that she might never see him again. Clark is the love of her life, her soulmate, and her greatest ally in the fight against injustice so leaving him is the hardest thing she’s ever had to do.
So with one passionate goodbye kiss, Clark sends Lois back to the present and thanks to her memories of this alternate timeline, she helps Clark to stop this disaster from ever coming to pass. This scene just goes to show you how Lois and Clark always come through the darkest of times and will continue to do so no matter what comes their way.