Neutral or Geno? Either way, I find Undyne a little easy. In PS!Outertale (I played Project Spacetime before Undertale), it took me 30ish deaths to take care of Undying Undyne and 20ish for Dark Neutral Undyne (dark neutral Undyne is harder than Genocide Undyne for some reason). Some of those skills stayed with me, because I only died 3 times against the actual Undyne the Undying on the PS4.