A pilot and weapons expert who was given a nickname for the worst thing she ever did, and has never corrected anyone about it.
Melinda Qiaolian May is a S.H.I.E.L.D. pilot and weapons expert, nicknamed the Cavalry against her wishes after a mission in Bahrain where she saved an entire S.H.I.E.L.D. team from a rogue Inhuman. Ming-Na Wen plays her.
She is the best-written character in that series and the reason is restraint: she says very little, and the show waits two seasons before explaining the nickname.
Minor spoiler
What S.H.I.E.L.D. does not know is how she saved them. She killed a young girl, Katya Belyakov, and she has not moved past it years later.