Why does my cat always be so mean to the other cats....!!!?

your cat is probably territorial of his 'property'. That can be his house and you. He probably doesn't want any other cats bothering you. Mine used to be just like that

The cat that is being "mean" is establishing the pecking order. One member of a group will always be stronger and smarter than the others. This is normal and unless the other cats are really getting physically hurt, I would not worry too much about it.

Marlou is right, but remember that cats are very territorial

your cat is jealous and dont not like to be *not* noticed try spending time withall of them equaly,not play with your fav cat or new cat.try and get them to be friends!it worked for me!

or it could be that your cat is territorial!

if it's a guy, they won't let anyone on their territory. even though the cats have a hierarchy where the girl is at the top, the girls aren't as territorial as guys.

Your cat may be trying to be dominant among the other felines.

Are all the cats spayed and neutered? If not, do so. It will help.

It's obvious, isn't it? He doesn't like anyone else on this turf.

sometimes its because they are bred from simese descendancy which are known to be moody

it might have agoraphobia