Board Thread:General Discussion/@comment-26347196-20160226031758/@comment-27701762-20160226060745

Perhaps I've been a bit confused by the explanation, but in order for this idea, or this version of it, to work, either A) Asriel and Chara would had to have planned on this whole thing happening (i.e. both of them dying, both being reincarnated in some way, and then waiting for a human to fall who could swap souls with Chara), or B) Flowey and Chara would have to communicate with one another to put together such a plan prior to Frisk falling down. (B) can't be true, since Chara is awakened by Frisk's presence ("Your power awakened me from death").

I think Chara's plan had to do with eliminating humanity. So when Asriel holds back and does not kill the villagers on the surface, and is mortally wounded as a result, the plan necessarily fails (not to mention the more immediate plan of destroying the barrier).

Getting to Chara's plan in Undertale, I think you're right that it has to do with the post-Genocide ending, though I think the plan is conceived once Chara is reawakened. It coincides with the original plan in that Chara wants to destroy humanity (and perhaps the monsters as well), but now a different tactic is needed.

If this is correct, then Flowey's machinations are independent of Chara's. I'd say that Flowey just wants to "play" with Frisk (who, of course, he thinks is Chara). Meaning either one of two things: joining Frisk as they murder everything in the Underground, or tricking them into the True Pacifist ending so he can gain the power to reset everything to when Frisk first falls down and start all over. He mentions in the Genocide route that Chara is unpredictable, which may imply that observing and messing with Frisk allows for an infinite set of possibilities that simply isn't possible with all of the monsters.

Which raises the question that, if Chara wants to destroy humanity, A) why is destroying the world insufficient, and B) why not just take over Frisk from the Genocide ending and destroy the barrier? My guess for (A) is that Chara is sadistic and wants the more pleasure of killing each person personally, while for (B) there is something about the nature of Chara's power that doesn't allow for the destruction of the barrier, though what that is exactly is unclear (my guess is magic, because magic solves all problems).