How can I flat that cell? Put it in a vice and press the whole pack together? By foil you mean that silver/grey wrap around the battery, right? It isn't ruptured, but it is like foulded double. It doesn't look not-factory, so that might be normal. Oh, and the dent smells a bit sore (And from what I've read here on the forum, that isn't good.)

A few new (better) pics to make it easier:





And another question; is it hard to de-solder the top cell of the pack?