Vanya Hargreeves is one of the children that Professor Hargreeves adopted in order to "save the world", whose original name was 00.07. She is considered among her siblings to be the youngest one. Unlike her brothers and sister, Vanya apparently has no power and is a common girl that according to her father can barely play the violin.
Vanya was born from a woman that had no signs of pregnancy like her siblings and was one of the few that Hargreeves found. All of the other kids Hargreeves adopted developed some kind of supernatural ability at a very young age, however Vanya was the only one that didn't had one. Due to this, she always grew up feeling different from the rest of her family. In fact, Hargreeves never encouraged her in any way and apparently never seemed to show any interest in her.
In "The day the Eiffel tower went Berserk" she wanted to go outside but her father just told her that she could not because there was nothing she could do. In other occasion she was frustrated because she couldn't even play well the violin and she broke it saying that she couldn't do anything. Them Pogo came to cheer her up telling her that she was special.
In her teenage years she went through a rebel phase, in which she seemed to be very connected to the Kraken to the point that they were in a punk-rock band. Still Kraken continued as a member of the Academy. After he left the band in an important moment due to a mission of the Academy, Vanya realized that that wasn't her place and decide to leave her home without saying it to anyone.
Vanya was living alone and had written a book called "My life as 00.07" where she showed how she felt and all she lived during her years with the Umbrella Academy. She received a call from someone that wanted to meet her. When she went to the appointment, she meet the Orchestra Verdammtem which was a sect that wanted to bring the end of the world through music, and wanted her to join them. At first she refused, but after going with her siblings during Doctor Terminal's robot attack and being rejected by Diego she came back wanting to destroy the world. However the Conductor wanted to awake her inner powers and explained her that he had read Hargreeves notes and he discovered that she was in fact the most dangerous of her siblings. Hargreeves had experimented with her so that she could not use her powers to destroy the world. After that the director washed her brain and make her awake her powers. During a performance to show her abilities she killed the Conductor and went to the academy. There she killed Pogo and destroyed Ben's statue. Later she started destroying the world with the orchestra, but the Umbrella Academy appeared to stop her. During their confrontation she cut Rumor's neck. After that Séance appeared (possessed by Hargreeves) with an orchestra to stop her. She stopped playing and started arguing with him, saying that she was going to end the world and he called that a tantrum, which after she started crying. That's when 00.05 shot her in the head and left her half dead. Séance proceeded to use his telekinesis to stop the meteorites. After that she lost her memories about who she was and was not able to walk again.
After all that had happened Vanya is been taken care of by her family even though she doesn't remenber them. At one point Rumor, (who is still mad at her) shows her all that she did. Vanya watches, horrified at all that she had done.
Later at the end of Dallas, Rumor appears hugging her trying to forgive her for what she did.
Vanya's powers are channeled through music. She is able to use incredible destructive forces by playing a note on her violin. These forces can be used for something as small as severing someones vocal chords or blowing another's brains out the back of their head with the force of a shotgun, to bringing about the apocalypse and causing a chunk of the moon to come crashing down.