Usually if its a bully in a community tank you would see for a few days to see how it plays out and if after thats it is still bad then removal. If you perhaps have a compatibility problem then, well...it's a compatibilty problem! Remove it!
But if you have a bully because you have not the requisite number of scool mates, then the answer may well be to buy more of them - see, it all depends on what we are talking about. No simple answer.