In the next episode when Alternative SHIELD finds out where Skye is they say
The one that Banner built?
This cabin was constructed by Bruce Banner, and it is assumed that as the Hulk he is the one who punched the dent in the wall. This makes sense particularly when you consider how large the dent is. It is much larger than a normal sized fist, which is what Captain America has.
Here we see Captain America's original steel shield after being punched by Red Skull (who basically has the same strength as him). You see it is a normal sized fist print.
After Banner abandoned it, the cabin apparently became a safe house for people with powers who may not have total control over themselves yet or were initially feared by SHIELD.
The only other person I could conceive of making an impression this large would be Abomination, but I highly doubt SHIELD would allow him to stay at a cabin somewhere.