How does the judicial branch balance the executive and legislative branches?

By checking if any laws passed abide the constitution

The judicial branch Can rule their actions as 'unconstitutional'

Explanation:

The Supreme court justices that made the decisions couldn't be fired by the President. So, if the president blatantly did something that violate the constitution, the judicial branch could easily ruled it out and fix it. This will limit the actions that the president can do and prevent the president from becoming to tyrannical.

The judicial branch could also do the same thing for the legislative branches. The legislative branch basically has the power to pass the law. But the judicial branch has the power to examine the law before it's passed to find out whether the law violate any rules / amendments written on the constitution.