* Transformers (2007): The Decepticons initially sought to acquire the Allspark, a powerful artifact that could create new Transformers and reshape the world. Ultimately, their goal shifted to conquering Earth and using its resources to rebuild their own planet, Cybertron.
* Transformers: Revenge of the Fallen (2009): The Decepticons sought to revive Megatron using the Sun Harvester, a device that could drain the Sun's energy. This would give them immense power and the ability to conquer Earth.
* Transformers: Dark of the Moon (2011): The Decepticons aimed to steal the "Ark", a spaceship containing a powerful weapon that could have devastated Earth. Their ultimate goal was to conquer Earth and establish a new Decepticon empire.
* Transformers: Age of Extinction (2014): The Decepticons aimed to take over Earth by using the technology of the Dinobots, ancient Transformers that could transform into dinosaurs. They also sought to acquire the Seed, a powerful artifact that could create new Transformers.
* Transformers: The Last Knight (2017): The Decepticons' objective remained somewhat ambiguous. They wanted to locate the Staff of Merlin, a powerful artifact that could manipulate space and time. This could potentially have been used to reshape the world to their liking.
It's important to note that each movie's specific objectives are often intertwined with Megatron's personal ambition for power and revenge.