Welcome to BYC. If you put your general location into your profile people can give better targeted advice when you ask questions.
For example, there are breeds that are common in a particular country that are rare or completely unknown in other countries.
Bad attitudes can occur in any breed, though some are more noted for it than others.
I've found Australorps, Marans, Wyandottes, and Brahmas to all be good flock citizens and also generally calm. There are many other such breeds.
Leghorns are notoriously "flighty", though some people prefer to call them active and alert. Rhode Island Reds are notorious for being dominant in the flock, which *can* lead to bullying of more timid breeds -- but not necessarily.
A single bird with an unusual characteristic such as foot feathers, a crest, or a different color of feathers *might* be picked on.
But in the end it all comes down to the personalities of the individual birds and, to some extent, the conditions they're kept in. Birds that are crowded into minimal space may turn into bullies when the same birds kept in generously over-sized facilities wouldn't have.