Explanation: The Catiline Conspiracy was an incident in which a Roman Senator, the titular Catiline, planned to overthrow the Republic by force. Cicero discovered this plot (not on his own), and in exposing it, contributed to the downfall of the conspiracy (though arguably it never really had a fighting chance). Cicero would proceed to not shut the fuck up about this for the rest of his political career, and oftentimes in Cicero's speeches you'll end with an aside along the lines of "And when I saved the Fatherland from Catiline..." A time-traveler who killed Catiline would doubtlessly spare countless future Latin and Classics students from having to read Cicero endlessly fellate himself over foiling the conspiracy!
Not a fan of the meme template but as an inversion I tolerate it.