Probably the saddest part about the destruction of the old Mother Base is that Nuke fell into the ocean with it
Also I can totally see Kaz frantically scrambling around the base looking for him while everything goes up in flames around him because Kaz is a fucking softie and he MUST SAVE THE GODDAMN CAT GODDAMN IT
Sometimes he has nightmares about not being able to save him and he wakes up crying over a fucking kitten