Thanks for your question. Hypothetically it is possible that a group of people could 'overthrow' the Australian Government; however it is important to note that Australia's political system since federation has always been characterised by stability. This stability would make a military coup style of take-over—as has occurred in other countries—highly unlikely.
The Australian Constitution makes no reference to 'overthrowing governments' or 'tyrannical' behaviour.
The Constitution outlines how the Australian Government is formed and how members of parliament are elected by the Australian people. There are many ways the Australian Government can be held accountable for their actions. For example, the Opposition scrutinises—closely examines— the work of the government in Parliament. The media also plays an important role in holding the Government to account. Ultimately, the fate of the Australian Government is determined by the Australian people when they cast their vote at a federal election.
You can find more ideas how you can have your say and contribute to the work of the Australian Parliament on the PEO website.