The Superman's iconic "shirt rip".
The most important thing that Superman II and Krypton season 2 have in common is that General Zod is the main villain. In Doomsday. In the season 2 finale, the civil war came to an end when Seg and Zod faced off at last.
After Zod's forces turn against him, Seg realizes that Zod won't surrender and decides to challenge him to a fight by saying, "General, would you care to step outside?" This scene is a direct reference to a pivotal moment in Superman II, where Reeve's Superman gave the same polite challenge to Terence Stamp's Zod.
Cameron Cuffe has been teasing (via CinemaBlend) that the season 2 finale contains his "tribute to Christopher Reeve". Cuffe's tribute to Reeve serves as one of the show's most targeted Easter eggs yet, directly honoring what many consider to be the quintessential Superman while also emboldening the mythology of Seg-El.
What makes the moment even better is how Zod responds to it. While Seg channeling his grandson is sure to please Superman fans, it earns a much different reaction from Zod, who may have even recognized the line. Enraged, Zod attacks Seg and tells him, "you think you are him! You think you are the Man of Steel! You are no Superman!" This suggests that, later on in Krypton's timeline, Superman may have spoken the same line to Zod - or, at the very least, the General fought the Last Son of Krypton. Whether or not that conflict was at all reminiscent of Superman II remains to be seen, but Krypton's story will hopefully continue in season 3.