Arwen

Arwen Undomiel, also known as the Evenstar, is an Elf from J.R.R. Tolkien's The Lord of the Rings. She is the daughter of Elrond and eventually the wife of Aragorn. She is beautiful, gentle, and presumably wise, or at least intelligent, as befits an Elf. While her character is not given as much in-depth description as some of the other members of the cast of LotR, she is definitely a sympathetic character. Which is why the way she is characterised in badfic is so inexplicable.

In Badfic
In badfic, Arwen is either competing with the Sue for Aragorn's manly affections, or braiding her hair and twittering about how wonderful Aragorn is, because the Sue is going after Legolas.

In Badslash
If Arwen appears in m/m slash, it is almost exclusively because one of the protagonists is Aragorn, and he is trying to escape her evil bitchy clutches. If the fic is femmeslash, then Arwen is usually slashed with Eowyn, Galadriel (who is her grandmother, not that that badslashers a) know that, or b) give a damn) or Rosie Cotton. All three of these pairings are bizarre and extremely unlikely, but femmeslashers in the Tolkien Fandom don't exactly have a lot of choice.