Board Thread:General Discussion/@comment-27524978-20160210030742/@comment-4383275-20160505034330

Stevethebarbarian wrote: ASRIEL answers the question himself.

He simply says that he is running out of time. He still has his emotions after Sans is returned to life, so he obvously dosen't have the emotions because he has Sans' human SOUL. 1. He still acts emotional as Flowey in his post-credits scene, though, so that doesn't add up.

2. Sans remembers every erased and existent timeline of Undertale. Moreover, specifically in the Genocide Run, there is some evidence that he doesn't have a soul of his own.

Firstly, all the Boss Monsters have their own SOUL Modes to match the six human souls except Sans.

Secondly, Sans describes his difficulty to "give it his all" during his fight, indicating a feeling of apathy. You know who else has a feeling of apathy shortly after being deprived of a soul? Flowey, right when he's created.

Plus, remember, Sans shows much less humanity and empathy during his Genocide fight than anywhere else in the game, offering to spare the player only to kill him shortly thereafter with a casual "getttttttttt dunked on!" That, by the way, mirror's Flowey's intro sequence, where he pretends to offer the player "friendliness pellets" only to use them to injure the player.