From 1789 to today, have as many coups, revolutions, overthrows, civil wars, etc. as possible in France. Whether it's Bourbon, Bonapart, Orleanist, Republican, Boulangist, fascist, communist, or whatever it may be.
1830 Revolution be more successful, King Charles X doesn't give in like King Louis XVI, he gets overthrown. The resulting turmoil causes an years long civil war between the many factions of France, some of them listed on there. In the end, a tenable democracy is formed, only for one particular Bonaparte to take over. A disastrous war against Prussia when they both intervene in the alt-Swiss Civil War forces Emperor Napoleon III to abdicate. A Bourbon king replaces it, but the Orleanists do not like that and start another civil war (similar to OTL Carlist War in Spain). Whatever comes next only lasts a few years before the socialists come in and take over the country from within. Changing alliances and a powder keg in the African colonies causes a major European war, in which France was on the losing side. All this time, French Algerians have slowly been moving into southern France. A government similar to OTL's Weimar Germany forms, only to see the rise of a fanatical Fascist leader rise in France. Algerians, prosecuted under the new government, start to revolt. Since there are now many Algerians in southern France, it starts another civll war. The civil war wasn't finished when another fascist country invades France, forcing the two sides to ally with one another. France eventually beats them back, before descending into civil war again. Eventually, an third faction in the civil war, the communists, gain power and force a totalitarian state in France. A few years pass before pro-democracy protests start to happen, which devolves into a civil war. In the end, the pro-democracy side wins, only for a Christian fundamentalist group to take over and start a theocracy. State supported attempts to kidnap the Pope succeed, causing a 20th Century antipope. Also, state-supported Catholic terrorism happens against Protestant, Orthodox, Islamic, and other countries. Islamic terrorism counterattack on French grounds, using Algerian immigrants into France. After a while, the two terrorist groups start a civil war in France. The civil war splinters further until France enters a warlord era. One of the "warlords" is a long-term monarchist. After conquering all the other warlords in France, he crowns himself king, only to be assassinated by his pro-Prussian best friend. Afterwards, his best friend asks a Hohenzollern to take the throne of France, and was pretty popular among the French public who were willing to end the conflict, ending two centuries of turmoil in France.
I'm seriously not sure how plausible this might even be (This might even be ASB), but this has to be the greatest French-screw ever.