Do famous people always exert positive influence on society?Do you have any examples of famous people having negative in

Of course not.
Famous prople,heroes or bad people, both have influenced history.In other words,some famous people,such as Chairman Mao *,founded the new republic.
People who brought negative influence on society existed here and there,such as Hitler,who set the anti-human war.Other example such as Yuan shikai,the fake president of early China,Chen Shuibian ,the fomer * "President"andso on .