1. Look what has come of it!
2. Look what has come out of it!
I would use #1 in the sense of "what it has become, developed into, or grown to be". I would use #2 in the sense of "what has resulted from it, or been produced from it". A separate meaning for #2 would be (if it were an egg or a box) "look what came from that container or egg".
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I would use #1 in the sense of "what it has become, developed into, or grown to be".
I would use #2 in the sense of "what has resulted from it, or been produced from it".
A separate meaning for #2 would be (if it were an egg or a box) "look what came from that container or egg".