I'm not sure whether this is more of a debate or theory thread, but I think it deserves to be discussed regardless.
In the Dark Kingdom Arc we see Usagi take out both Beryl and Metallia. However, when we get to the Black Moon arc and are shown Crystal Tokyo, NQS didn't take out Wiseman, because he was human (Fine, Death Phantom.). We see something similar occur in relation to Usagis hesitance to take out Prof.Tomoe in Infinity, though that may have to do with his being Hotaru's father (Can Usagi not access her previous attacks? I seem to recall her still being able to use her tiara as a boomerang after the events of the Dark Kingdom.). However, that being the case (and this may tie into my reincarnation and time loop threads.), what changed between the events of the Dark Kingdom Arc -> Crystal Tokyo (removing the Dark Moon Arc) that forced Usagi to change her stance on eliminating enemies once she became Neo-Queen Serenity?
This among other reasons leads me to suspect that ChibiUsa's time travel forced a number of changes to the original timeline to occur which forced Sailor Cosmos to travel back in time to try to persuade Usagi to destroy the Galaxy Cauldron.
I'm still attempting to flesh this out, but I suspect that there is something to this. I sincerely do believe that ChibUsa's time travel created a wormhole of sorts which allowed figures like Nehelenia to escape to the future (To gather the Amazon Orbs) and travel into the present (Seriously, someone needs to have a chat with Pluto...). I'd say the same is *possibly* true with Shadow Galaxia considering Sailor Animamate Tin Nyanko's exchange with Luna and Artemis. Their planet had already been destroyed during Silver Millennium, how then would Luna and Artemis know that Sailor Animamate Tin Nyanko was not the real Sailor Mau?
This does bring up something interesting, though, Guardian Cosmos informed Usagi that Chaos would revive anew in the 30th century AD. We already get a glimpse into the future with the rise of Wiseman/Death Phantom in the 30th century, and considering that he's already been taken out during Usagi's journey to the future, who then is this new threat?