Warning: Some of these are pretty dark. You have been warned.

Loki:

One of your fellow agents, Anna, was a very good friend of yours. Until one day, when she went on a mission and never came back. Loki was shocked to see you crying when you cane to do your shift, and later he got one of his visits out and got an ice cream with you to try to cheer you up. Even though he hates ice cream because no matter what colour it is, his tongue goes blue.

Tony:

Your older brother was hit by a drunk driver and killed. Tony had to be the one to tell you, and you burst into tears and then cried with him all day, watching comedy movies in an attempt to laugh. He was friends with your brother too.

Steve:

Your dog died. That might not have seemed like as big a thing as a person dying to some people, but that dog really meant a lot to you. Steve helped you bury him and then you co-authored a poem in his memory.

Clint:

No matter what this was, it would be a double blow, because Clint knew almost everybody that you knew. When your two little twin sisters went to a theme park, you never thought anything of it; that is, until the ride they were on crashed, killing one and leaving the other in a wheelchair. Since they were like sisters to him too, you had to keep each other strong, but you kept going and hid your tears from Y/S/N.

[I don't feel bad. At. All. Except I do. Dammit, conscience!]

Bruce:

There was an extra Avenger on the team for a while. She wasn't there for long, not even long enough for the public to give her a "superhero name". Because after a very short time, she was killed, on the very last of the new Hydra bases that had sprung up. It shocked and grieved the entire team, but especially you, because you were good friends and also as manager you felt a little responsible. Like always, Bruce was wonderful and was right there whenever you needed him.

Bucky:

You weren't exactly close, but when one of your patients committed suicide you felt as if you'd personally failed him. You were the psychiatrist, and you let him down. Bucky kept you going through it with constant support and reminders that it wasn't your fault. Some damage was beyond what your work could heal.

Pietro:

Your mother had recently been very sick, as you may remember from the last chapter, and unfortunately after a month or two there was nothing the doctors could do. Pietro kept you cheerful when the loss of your beloved mother could've led to depression and having to regularly see Bucky's girlfriend, the psychiatrist. Apparently she wasn't very good anyway; you'd heard one of her patients had committed suicide the other week.