From all the books that I have read, and all the characters contained within them, Scythe Anastasia Romanov from Thunderhead is the most likely to be able to make a wow moment, in my opinion
Over the course of the series (Scythe and Thunderhead are two books in a series), we see Citra Terranova evolve into Scythe Anastasia. Not only does she take on a new name in this process, but her demeanour completely shifts as well. The apprenticeship that she undergoes in the first book change who she is as a person. She goes from someone who is stubborn, yet deferential to someone who is perfectly willing to take charge of any situation she finds herself in. This shift in personality over the course of the books means that while Citra from Scythe would not someone I think could make a "wow" moment, her new self definitely is.
Another thing that makes her capable of making a "wow" moment is her passion for upholding the resigned humility that was intended in the Scythedom's creation, against a wave of revolutionary thinking that is taking over throughout the course of the books. We see this passion to keep the old ways in motion throughout Thunderhead, as she works to combat the grabs at power by the scythes who choose to be more cruel in their methods. She is pictured throughout the book as an idol for her intense love of what the Scythedom should be, and her defense of what it is becoming.
The Scythes with whom she apprenticed under are also an influence for this, Scythe Curie is definitely another character who I think could make a "wow" moment, and this attitude is something that Scythe Anastasia inherits from her mentor.
Overall, with all factors considered I think that Scythe Anastasia would be the best candidate from the books that I have read to create a "wow" moment of her own.