Tony -

His reaction was quite predictable and he was a lot worse than you were

Steve -

He held your hand throughout the whole time and lovingly stroked your hair

Clint -

He seemed very calm on the outside but his eyes showed just how panicky he really was

Bruce - 

Thankfully, he was very calm and organised throughout

Thor -

He stayed in the corner of the room, cringing, but he encouraged you best he could

Loki -

He was traumatized by the entire experience