your vriska post confirms my idea that Undyne, despite what a lot of people joke about, REALLY isn't a Vriska personality at all. Not the least that she is an unambiguously Good person (Battle Against a True Hero and all), but the whole thing about her is that she is a shoenen protagonist about fighting evil with a heart of justice, but she doesn't really value victory for her own sake, or to be the best; her motivation is protecting people and she's very selfless. Any true Vriska is a LONG way from the specific kind of mindset and outlook required to be an Undyne!
I think that, like, Aesthetically she's a Vriska, and she has a histrionicness that is very Vriska, but Yeah, personality wise she doesn't ping much(and Im not Learned on Undertale lore, so idk how she'd fit backgroundwise).
I WOULD accept her as a "Good/Heroic/Moral Vriska" however, as I don't necessarily think Vriskas HAVE to be as nefarious and destructive as Vriska Serket is(another "good vriska", imo, would be the OG Vriska: Hakubi Ryoko from Tenshi Muyo u_u u_u)











