My gosh there's a lot of difficult ones for coloraturas out there. A big part of being a coloratura soprano is being able to do all those acrobatic melismas and jumps:
The most difficult arias for coloratura sopranos:
-Popoli Di Tessaglia (G#6) Mozart concert aria for soprano
-O zittre nicht Mein Lieber Sohn-The Queen of the Night's first aria from Mozart's opera Die Zauberflote (one F6) The high F isn't even the most difficult part if your a natural coloratura. The hardest part is the Bb5 section overall where it has the extensive coloratura section, which yes just so happens to end on the F6 at the end. You have to have great breath control to make it even less than halfway through the coloratura melismas. Unlike the more staccato coloratura passages in the Queen of the Night's second renowned aria, Der Holle Rache, O zittre nicht has more lyrical beginning, and legato coloratura passages. Besides, the tessitura of this aria goes up to a Bb5.
-Der Holle Rache (4 F6s that I've counted) I've never learned either of the Queen's arias, but I have them in a songbook. I counted four F6's in Der Holle Rache). Once again, it's not the F6's that are the super hard part (I can hit those), it's the sheer power, drama, and high tessitura that comes with great coloratura control at that high pitch. This is the Queen's big "Drama Queen" song literally.
-Martern Aller Arten Konstanze's second aria from Mozart's opera Die Entfuhrung aus dem Serail- Another dramatic coloratura aria. It only goes up to a D6, which is often a high note for many lyric sopranos. However, there aren't many lyric sopranos could ever sing this coloratura aria. It's a lovely aria that goes up and down quickly with coloratura melismas. As Salieri puts it in the Amadeus movie this aria is "10 minutes of ghastly scales whizzing up and down like fireworks." Of course, I disagree with the "ghastly" part, I think this aria is fantastic and beautiful, but those quick scales whiz zing up and down certainly wouldn't be an easy feat at a tessitura that reaches a C6.
-The dramatic coloratura version of Sempre Libera from La Traviata- it has Eb6 flats and 13 descending high C6s
-I don't know much about this opera or the arias from it, but Lucia's arias from Lucia di Lamermoor (Il suono dolce, I think goes to an Eb6-E6
-Caro Nome (B3-C#6/Db6) from Verdi's Rigoletto I haven't learned to sing this one yet, but when I have more technique I hope to learn it. It has a mixed tessitura going up to an A5 this aria is light, almost ethereal, and very difficult. A great amount of air required to sing this. It has an almost an "airy" sound, but not quite because the words must be articulate and the air flow properly controlled. This is an aria that most coloratura soprano
singers, even the most famous professionally trained opera singers, don't usually learn to sing until they are in their mid 20s to early 30s. I think that it has to do with having the ability to sound light and youthful, but also dark and mature at the same time. There aren't many young coloratura sopranos under the age of 25 who have fully matured voices. Either way, when I search on Youtube this aria is rarely chosen for college students voice recitals.
Ah! Jeux Veux Vivre from Gounod's Romeo et Juliette (D6)- Not one that I've learned yet, but it's still one that I want to learn at some point in college when I'm ready. This aria uses chromatic scales in coloratura melismas that go up and down. It doesn't necessarily require as much air as Caro Nome, but this aria is still difficult due to the long coloratura melismas.
Virgin Classics' two-disc SACD collection of arias, scenes, and songs from Natalie Dessay's complete opera recordings and recital CDs is notable for its variety and contains some rarities, such as excerpts from Meyerbeer's Le pardon de Ploërmel and Offenbach's Robinson Crusoë, as well as standard repertoire. The first disc is devoted to French opera and operetta (if you count Lucie de Lammermoor as French). The second disc includes music by Mozart (arias for both Pamina and the Queen of the Night), Handel, Richard Strauss, Stravinsky, Thelonius Monk, and Leonard Bernstein, among others. Dessay's light and silvery coloratura is remarkably secure throughout her range and is especially brilliant in the stratospheric reaches, an attribute that makes her "Bell Song" from Lakmé and Olympia's song from Les Contes d'Hoffmann truly spectacular. Her performance of Pamina's "Ach! Ich fühl's," is deeply emotional and is as persuasive as the Queen of the Night's "Der Hölle Rache." The limpidity of the Handel aria demonstrates her mastery of an emotional world far from the pyrotechnics of French grand opera. She is equally at ease in the newer repertoire, an understated obbligato part for a French adaptation of Monk's "'Round Midnight" and Bernstein's "Glitter and be gay," which showcases her gifts as a comedian, and to which her accent adds a charming dimension. Dessay makes a strong case even in roles that generally feature a voice with more weight, such as Manon. The many orchestras, choruses, and soloists that accompany her offer strong support. The sound throughout is clean and bright.