Post 19th Century Italy - They were bad, just flat out bad. So bad that they had to go beat up some poor Africans with sticks just to suppress their insecurities. Their struggle in Greece is a cute little story that unfortunately gets ignored nowadays.
Austria-Hungary - Probably the least deserving of the bunch, and they usually got places due to diplomacy. A lackluster performance in WW1 pretty much sums up their military competency.
Russia - If they didn't win the majority of the fucking time, they would probably be the worst, but cracking a Russian's spirit is like trying to split carbon steel pipe material with a Home Depot chainsaw. Russia's successes in warfare are undeniable, but the statistics speak for themselves.
Paraguay - They almost got their entire male population wiped out in a single war, essentially plunging them into an all-around hellhole of a place to live for the next 50-60 years. Offensive momentum was lost in less than six months, and their naval tactics were laughable. Paraguay's conventional and guerrilla strategies were complete fucking disasters and should be one of the textbook examples on how not to conduct warfare on a large scale.
Byzantine - Obviously not a country, but they were bad for the majority of their existence. Besides our god tier savior Justinian, it was pretty much a back and forth struggle between shitty and mediocre to decent emperors. Even then with a few bright spots it didn't go down so well. They rarely expanded outside of a few stints in the late 12th and 11th centuries, not to mention they got saved from the Seljuks by the Crusades (and then got fucked over by said crusaders and Venice the fourth time around). Outstanding military, fire that can't be put out by conventional means, sexy architecture, a near unconquerable city, and a badass Scandinavian/Slavic personal bodyguard? Check. Shitty management of said army, loss of knowledge on how to create cool fire, conversion of architecture to a gigantic mosque plastered with crescents, Turks in general, and badass guards that I can't really downplay because they were actually very critical to the limited Byzantine success? Check.
Regarding France, I think people are mixing up losing a war and just plain sucking dick at fighting in general. Research will show that France has the best battle record of any nation, with at least 750 victories and 400 defeats. Look no further than that Corsican/Italian/French dude (Napoleon, derp) that beat back 3 (technically 4 if you count his time before the coup) coalitions of some of the most powerful empires to ever walk the earth. Guess what? He still lost the eponymous Napoleonic Wars, but managed to rack up enough tactical masterpieces to show that France wasn't a bunch of angry bourgeoise-esque peasants armed with pitchforks and last week's bread. Even well before Napoleon, France was dominating the scene as a superb military power with extensive reforms and tactics that are studied to this very day, which is pretty hard to do since some of this shit is outdated by 800 years. French soldiers have put up fights that rival what you would hear about the Poles and Spartans, and they certainly didn't sit around eating sandwiches and painting abstract art all day. They rivaled Britain and Spain at one point in terms of colonial expansion and army prowess, and essentially dominated European geopolitics from the late 18th to the early 19th centuries. France lost many wars, but has won a fair few as well.
I think the stigmatization comes from France undeniably being dreadful at warfare the past 150 years. The Franco-Prussian War was a disaster, WW1 didn't go well for either side, and they got dunked on during WW2 in 40 days. They also had their fair share of losses before and after the 19th century (Spanish Succession, Seven Years War, Indochina, etc...) but that doesn't discount their successes in any way. Overall, they ain't shit at warfare, but running away after the Ardennes was infiltrated didn't help.