False Light: I Would Like to Know the Consequences of Defmation Said in One Country

My question involves defamation in the state of: Slander without any proof or evidence and testimonys only from memory and nothing in writing. What are the consequences of someone making this slander public over social media websites such as twitter etc. and the person who the slander is being brought upon lives in australlia what would be the ramifications of such an action in this country another European country and maybe even a third world country. Hopefully slander involving racial incitement and other negative things.

False Light: I Would Like to Know the Consequences of Defmation Said in One Country