The next in line is…
Undyne! :D
It is similar to the original version in many ways, but there are a lot of "buts". (I'll talk about some of the main distinguishing features for now)
1 - Because of the harsher world, Undyne has also become harsher.
No mercy! Unquestioning execution of orders.
"You" will be saved only by a scientist. (Either Alphys or Papyrus, while the branch of the story is not so accurately spelled out ..)
2 - In the course of history, she is already with Alphys. They don't hide it. (Although the fish is less talkative about it)
3 - Her left eye was gouged out by Sans himself. (It happened when she challenged him to a sparring match and crossed the line on emotion, a kind of punishment for breaking the rules.) They're more than just not getting along.
4 - She avoids Papyrus, they stopped being friends here a long time ago. (Although they are not enemies, Undyne will never say anything bad about the royal scientist, that even after the experience he got back on his feet and achieved extraordinary heights, she even admires him. Rather, she's just afraid to hurt him or hurt him in any way. She feels guilty that, as a child, she didn't even notice his "disappearance" from her usual days, she didn't notice something was amiss…)