Being asked to Join a Team

A new person is going to join Coulson's little team. She is vicious and full of blood lust but is very easy to get along with. She is beautiful , powerful and is best friends with the Avengers. She is the highest rank and harder to kill than Deadpool.
And she is going to cause such Chaos in the Team but she will happily make their lives miserable if she wanted too. Luckily she likes them. Well that is not much better.
This story happens after the first episode in season 1. So get ready! Also this is a Ward love story!