I love gouramis, and have four at the moment with minimal probs, just a bit of chasing each other. They live in a four ft tank with angels, serpae tetras, some bolivian rams and some fighters.
but I did have one golden gourami that killed two swordtails once. he was in the tank first and got territorial I think, it was awful, he would grab hold of their sword and pull them out from where they were hiding (trying to get away from him!!) and then nip them. He completely stripped them of their scales on part of their body.
I ended up taking him back to the LFS and swapping him for another fish. I think it can depend on the size of the tank too, as this guy was in my smaller tank (60L) which may not have been big enough for him and a couple of swordtails (forgive me I was a new fishkeeper at the time :oops: )