HIT IT said:
I'd say that if Sans can't hurt her, this is a stomp thread, since there's no way he could ever win in a million years.
If Sans can hurt her, then by extension he can destroy her essence and... I ran a speed calculation just for this.
If Undertale battles took place in normal time. Light would travel 9993.08 kilometers per frame.
The speed of light in an actual Undertale fight Assuming Frisk's soul is 5ft in diameter (which is highballing it, the lower this number is the stronger timescale gets). Light travels .0001016 kilometers per frame.
Meaning the timescale of an Undertale fight is... 983578866.61x
29,507,365,998.3 'frames' per actual second.
Beatrice moves .00367% the speed of sans, subtracting 108292033.213761 damage from the total.
This leaves a total of 29,399,073,965.08624 damage with no KR factored, per second.
29,399,073,965.08624 damage is enough to obliterate 296,960,343 Chara/Frisk Fusions AFTER they'd already killed Sans and gotten the power boost from that that allowed Chara to oneshot an entire multiverse. That is to say, after they became capable of existing outside of a multiverse.
Sans Speedblitz's Beatrice from his damage per second (base with minor KR), and Reaction speed/Combat Speed being massively superior. Or he can't hurt her and this is a stomp thread. take your pick.
I think that Sans COULD hurt her, because of his ridiculous ability to ignore defenses on multiverse+ level beings up to and including 'invulnerability frames', but that's just my take on the matter. My vote is for Sans, because I think he could do it before she could react.