So I think that A battle between Sakuya Izayoi vs Sans is going to result in this. Sakuya Izayoi is as fast as Sans as she is as fast as light. Sans and Sakuya Izayoi aren't really going to get tired but Sakuya's fight can last very very long but for Sans that is a different story as he does show signs of getting tired. And tapping Sans will kill him so he would also die if Sans fell this means that Sans is very careful and aware of his surroundings.And for Sakuya she has a lot of HP. Sans can mess with timelines and Sakuya can mess with time.And so I think that Sakuya would win not Sans.Because the only thing that is arguably a better power is timelines vs time.[1]

  1. I'm sorry I can't put in images sorry if you wanted images.