Hugest

[Xinfu]

When John hears a ridiculous thing, can he say this?:

-This is the hugest joke I've ever heard in my life.

[Rusty]

Yes, but a ridiculous thing isn't always equated to a joke.

[Xinfu]

Thank you~

Then what would be those natural English expressions used by a native speaker?

[Rusty]

That's the most ridiculous thing I've ever heard (in my life). (anything that seems preposterous or absurd)

The biggest joke ever played on someone else was ... (a prank/a practical joke)

I just heard the funniest joke ever. (a humorous story/quip)

[Xinfu]

Thank you~