Asriel didn't know about Chara's motives for being an omnicidal psychopath, and there was no manifestation of Chara whatsoever during the true ending boss fight, even though there were plenty of monster AND human souls present.
Flowey had powers because he got injected with heaps of Determination (which was what created him), not Chara.
You're conflating the "The player is Chara" with "The player is influencing Frisk". The player is not Chara, and people most likely think so because so many people put their names on the "Name the fallen human" screen and take it as a hint.
[Citation Needed]
1.- Because by that point it can be assumed that Frisk ridded of Chara's influence and the final boss was more or less 100% Asriel, he even thinks Frisk is Chara, and the he clearly realizes Chara is gone from there, i think it could be interpreted as either ridding of Chara for ever, or Chara just not being there at all.
2.- If that was so, how come He lost them when Frisk showed up? Before you say "Frisk was more determined", then how come Flowey took the save powers back when he had 6 Souls, how does that make him more determined than Frisk? the only difference between Frisk and Flowey in that moment was that Flowey had more souls, not more determination.
3.- Chara exists both as an in universe character and as a metaphor for the player's drive to run games into the ground, mentioning the metaphorical elements of the character of Chara makes it easier to explain why my theory is that Chara is trying to influence Frisk during all runs, and not only Hog Wild, the player's actions just determine how much story wise Chara succeeded in influencing Frisk.
4.- Refer to #2, We're just sharing theories here.
2.- If that was so, how come He lost them when Frisk showed up? Before you say "Frisk was more determined", then how come Flowey took the save powers back when he had 6 Souls, how does that make him more determined than Frisk? the only difference between Frisk and Flowey in that moment was that Flowey had more souls, not more determination.
3.- Chara exists both as an in universe character and as a metaphor for the player's drive to run games into the ground, mentioning the metaphorical elements of the character of Chara makes it easier to explain why my theory is that Chara is trying to influence Frisk during all runs, and not only Hog Wild, the player's actions just determine how much story wise Chara succeeded in influencing Frisk.
4.- Refer to #2, We're just sharing theories here.
I took that line as him saying "thanks to these sequences of events, i eventually became a soulless flower" as in if he did kill those humans, he would have never became a flower.
To me it felt like
"I turned into something that couldn't possibly hurt anyone" but then came Alphys...