I know there are some theories about what happens in Soulless Pacifist and what Chara is up to (genuinely out to kill and maybe has already killed? passive aggressive little pissbaby getting in a Sans-style passive aggressive parting shot?), but what if BOTH were true?

Chara is genuinely corrupted and dead inside, just playing along until they can kill on the Surface because that's their purpose, that's the only meaning they can get out of what they've seen and experienced, they can't connect to these people anymore

and how CAN they

Toriel looks through them

Asgore won't even say their name

They're a ghost, unanchored and adrift, unloved and unwanted, tied to a heartless higher being who plays with all its toys and breaks them and doesn't care.

So why should they?

And then

Asriel tells them how much he loves them.

Asriel keeps calling them by name, and keeps telling them how much he loves them.

And Asriel starts crying.

(They hate seeing him cry.)

Until even THIS Lost Soul, turned twisted and made malignant, starts to remember.

How he found them.

How he saved them.

Being a family…

So when Frisk calls out one last time, it SAVES two Lost SOULs simultaneously - like Sans and Papyrus, like Asgore and Toriel - and Chara and Asriel.

(Asriel SAVEs Chara AND the world without even knowing it. Through the power of being a crybaby. GOATed.)

(Not pictured: Chara, snapped back to their old self and now in an emotional tailspin of guilt and anger and other complicated emotions over what they did, lets it out in the most emotionally healthy and constructive manner possible! Tormenting their "partner" with creepy faces and creepy photos to guilt-trip them into leaving, because that always makes Chara feel better >=))