Inertia is the tendency of an object to resist changes in its motion. The more massive an object is, the more inertia it has. So, the objects with the most inertia are the most massive objects in the universe.

Here are some examples:

* Stars: Stars are incredibly massive objects, with the most massive stars containing hundreds of times the mass of our sun.

* Black Holes: Black holes are the densest objects in the universe, containing immense amounts of mass packed into a very small space.

* Planets: Planets are also massive objects, with Jupiter, the largest planet in our solar system, having a mass of about 318 times that of Earth.

* Galaxies: Galaxies are massive collections of stars, gas, and dust, and can contain trillions of stars.

It's important to remember that inertia is not just about mass. It's also affected by how the object is moving. For example, a spinning object has more inertia than a stationary object, even if they have the same mass.

Ultimately, the object with the most inertia is the one that has the most mass and is moving the fastest.