Final line from David Lean's 1957 "Bridge on the River Kwai," has always stuck with me:

[last lines]

Major Clipton: "Madness! Madness!"

And near the end, a line where the main character finally realizes the enormity of his foolishness (which should apply more to intransigent Republican politicians and Trump voters than it ever will to Trump and Musk themselves):

Colonel Nicholson: "What have I done?"