Tell me what happens if your kid has a bad attitude?

Hard to say. Not knowing what "bad attitude" means for this child, hard to give a meaningful answer. In general, others react poorly to a child who is not "with the program, " which can mean social isolation from peers, disciplinary action from teachers, & strained relationships with parents, siblings, and relatives. Understanding the cause can be a start; probably could benefit from professional assessment.
That depends on you. See a behavioral therapist, who will explore family dynamics, parenting style, school problems & difficulty with peers. Set clear rules for behaviors you expect. Consistently use immediate reinforcers for those you want & consequences for those you don't want. Don't engage in arguing or show anger. Positive or negative attention reinforces behaviors. Ignoring behaviors makes them go away.