Steve:
When you have a nightmare, you stand up immediately, and then sit down again. Steve holds you in his arms while you talk about what happened.
Tony:
You punch Tony in the face on accident when you have a nightmare, so you press ice against his face while he comforts you.
Thor:
He wraps you in a bear hug when you have a nightmare, and you bury your face into his shoulder. Then he brings you to his chest and tells you to try and sleep.
Clint:
He takes you to the roof of Avengers tower, and he holds you while you calm down. Eventually he carries you back down to bed because your sleeping.
Bruce:
He pulls you into a kiss, and then tells you to think of other happy things, not the nightmare. You guys then talk about the memories you're thinking of.
Natasha:
When you have a nightmare, you need to let it out, so you scream in your pillow. And then you drag Natasha to train, and she happily agrees. She trains with you until your tired again.
Pietro:
He kisses your face, and hugs you. If you're crying, he kisses your tears away and then kisses your lips. Then he orders you to try and sleep again, with you in his arms. You soon fall asleep after that, happy in his arms.
Wanda:
She hugs you, telling you reassuring things in your ear. Like, "it's okay," and "it was just a dream." You eventually feel better after a bit.
Bucky:
Sometimes you have nightmares together, so you cry in each other's arms. Otherwise, he hugs you and kisses your forehead.
Loki:
He hugs you and strokes your hair, telling you it was just a dream.