Alphys also concealed her accidental discovery of the tapes hinting at Chara's nature. They don't make Chara look too good, for sure, especially laughing at Asgore's accidental poisoning. But I can think of different kinds of laughter, not all of them meaning the same thing...

I'll reiterate my view of Chara's "plan" (summed up here: https://witches.town/@kara_dreamer/3365143) wasn't a grand scheme to destroy humanity but just Chara's hasty bolt for the exit. And they had to lie about the purpose to get Asriel to go along. So Chara's a shit, sure...but not _that_ awful a shit. In my opinion.

#Undertale