What is the most extreme check that congress has on the President?

Impeachment

Explanation:

Congress can remove a President from office if there is a belief amongst lawmakers that the President is no longer fit to hold power.

The House of Representatives will vote to impeach the president and if a majority vote for the impeachment, the President will be impeached after which the process passes to the Senate which then holds a trial and votes on removing the President.

If two-thirds of the Senate present votes to remove the President, the President will be removed from power.

the declaration states, “we hold these truths to be self-evident, that all men are created equal, that they are endowed by their creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness….”

for your question the answer would have to be france