These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
( After seeing the full ending, serveral people have suggested that Kachi/Achi was only pretending to have lost her memory.)
Although it could be said that it's not just an alternative interpretation, since her tone when she reveals her identity suggests that she was faking all along.
But that's something along the lines of Dubtext as the tone change isn't present in the original Japanese recording.
The backstory as explained in the European website further suggests that her amnesia was genuine. Her realizing that she has no memories is given in 3rd-person omniscient narrator form, and happens before she meets Isa.
With Kachi's reveal, it's possible that the Nebulox are actually the good guys. Even though they are brutal, they were genuinely trying to protect their home from an extremely dangerous enemy who caused countless deaths and much damage.
However, it could be that Achi/Kachi had the right idea in the first place. She could have been trying to free humanity from the creators, because they were brutal. Every time humanity tried to use diplomacy, they were wiped out. The creators just wanted war.
Not to mention another moment in which you kill a massive boss only to see it spit a newborn baby version of itself out of its mouth. This newborn instantaneously seizes control of a crane, grabs your partner, and then attempts to submerge them in lava. You free your partner and then dispose of the little twerp. Why did it do this? How? What...never mind. It was just goofy.
Crowning Moment of Awesome: (There's quite a few, including the player blasting the first Nebulox to their partner, who finishes them with a kick or slash, punching out Deko in hand-to-hand combat, Isa's transformation, and Isa vowing to defend Kachi's heart for the very final part.
(The character models and voice acting are good sources of this.
The scene in Stage 2 where Kachi asks Isa what "human" means. Dear god...
[Isa confirms for Kachi that humans have a head, two arms, two legs etc.]
Kachi: Oh, and a tail.
[Beat Awkward silence]
Isa: We don't have tails! [Both laugh.]
Stage 4, just about anything Ariana Shami says, especially "My Blood...is on FAH-YUUUUUUUUUUUUR!"
Narm Charm: (There are those who like the blood on fire line.)
Nightmare Fuel: (The battle with the Infant Keeper in Stage 6, where your partner is being lowered by a crane into slowly-rising lava and you have to raise a pair of platforms to keep up with the lava while occasionally stunning the Infant Keeper to force him to knock your partner back up. If you fail to keep up, your partner is SHOWN BEING DUMPED INTO THE LAVA, resulting in a Game Over.)