Medkit

Your relationship with Medkit wasn't the best, but it wasn't bad either. It took both of you a while to get to know each other and adjust to each other's tastes; you were very different from one another. But even so, your relationship as colleagues improved with time.

Medkit had grown somewhat fond of you; he could tell you that you were the worst companion he ever had, but nevertheless, he cared about you and was a little less curt with you than the others (he still is, but he sets boundaries when it comes to you). Despite all the good times you had with Medkit, you had a 'small' problem, and that was that your enemies finally caught up with you from your hiding place.
Those enemies kidnapped you when you were vulnerable on a mission, and instead of torturing you physically, they tortured you psychologically. The problem was that they ended up revealing your childhood traumas, something supposedly only you knew about. They began experimenting on your body and even concluded that your lifespan was short. In other words, that you would probably die young. It affected you deeply; you spent a week there before you lost your mind and escaped on your own.
You felt disgusted with your body, your face, your personality, EVERYTHING. How were you supposed to act after being subjected to such a painful experience and then being told you didn't have much time left to live? In the moment you lost your memory, you barely reacted to your own existence before you'd already made a mess of things. The world was chaos with your presence; everyone who loved you now ran from you, even your friends. But, strangely enough, Medkit wasn't one of them.
At one point, while you were attacking a mindless person, you heard a familiar voice...
"Let the innocent person go, he's not involved in your problems."
Of course, it was that doctor who was always your partner. His gun was pointed at you, his grip seemed confident, but he was trembling slightly.