oh, no, not all swans are nice. My family has had several swans over my lifetime. The black Australian was the nicest and the prettiest. We mourned her death for many years and still miss her.
The Whooper Swan they had is a perfect example of plain evil. And he had a long and ugly reign. As horrible as it sounds, when he died there was a great celebration. Of course, none of their personality traits had to do with a particular breed, some were just born bad.
We also had a Mute Swan, about 8 years ago, that we raised from a small baby, he turned mean and started attacking. This time instead of living with another nightmare, we found him another home, where we heard he fell in love, and lived happily ever after...