I think it's been established that SCP-682 doesn't have a soul.
He managed to be "killed" by being transformed into a grey and black liquid, but then to suddenly rise and attack the Class D's sent to verify the creatures termination, SCP-682 can develop temporary abilities like being able to emit a high pitched scream which can turn humans in a 15 meter radius to a "relaxed" state, can suddenly adapt to things.
The test with SCP-123 would not be continued if SCP-682 couldn't be totally incapacitated, have a potential to escape or sudden adaption.
Transmuted his skin cells to reflect a laser so it means he has biological manipulation and could reflect the lasers of gaster blasters, survived a reality warping book due to the fact it had the word "can" which means he can exploit weaknesses of any level, Can adapt itself to be organic or inorganic at will, further implying he isn't "living".
I think that once Sans manages to enrage SCP-682, or that 682 finds the fact that Sans is too fast for him to tag, he would adapt to find a way to kill or at least subdue Sans, as if he can't kill or destroy the thing attacking him, he always finds a way to subdue the said thing.
Note: He can also travel through pocket dimensions/Universes back to the original Universe if he gets BFR'ed. His way of inter-dimensional/universal travel is [REDACTED]