Yellowjacket is the name shared by two characters from the Marvel Universe.
Yellowjacket (Dr. Henry Pym)
Yellowjacket was one of the superheroic aliases of Dr. Henry Pym.
Yellowjacket (Rita DeMara)
Originally a criminal, Rita DeMara became Yellowjacket when she stole Henry Pym's Yellowjacket costume and modified it for her own use. Yellowjacket was recruited by Baron Zemo for his Masters of Evil, but later reformed and even became an honoary Avenger. However, she soon reverted to supervillainy, working with the Femizons and Doctor Octopus's Masters of Evil.
After Octopus' attack on Avengers Mansion led her into a battle with dopplegangers during the Infinity War, Yellowjacket met the 31st-century superheroes known as the Guardians of the Galaxy. When they returned to their native time (and timeline), she tagged along and joined the team. After many adventures, she finally travelled back to her home time.
Along the way, she encountered a future where the Avengers were enemies of the state. Seeking to help them, she came to warn the team after arriving in the modern age, only to be slain by a mind-controlled Iron Man.
As Yellowjacket, Rita possessed all of the abilities granted by the costume, including flight, the ability to shrink in size, and the ability to fire electrical blasts.