>>713392274
>Why is it better to kill one human, pass through the barrier and confront humanity to try to get six more souls than just kill whatever seven happen to fall into the underground?
Undertale states that a monster that absorbs a human soul is unstoppable.
Chara states that them + Asriel could've wiped out all the bloodlusted humans attacking them easily. A child was that strong, so imagine the strongest monster ever absorbing one. The underground and Asgore himself knows that Asriel was holding back as well.

>We also technically don't know how they all died
Asgore killed all 6 of them.