Don't worry, Stanton, IL MERCENARIO is in my Top 10 and I'm a huge Corbucci fan, so you won't find any sacrilege here.
Still, in my opinion being a fan doesn't mean I have to close my eyes for Corbucci's shortcomings. I called him brilliant when at his best, but very often careless or indisciplined. And Corbucci has an odd tendency to be more brilliant in his more flawed movies.
'I Crudeli' (The Hellbenders) has a brilliant opening and a devastating finale, but is plodding in between most of the time; 'Compañeros' is better balanced than 'The Mercenary', but it's also less lively and more aloof.
'The Mercenary' is visually stunning, ferociously violent, wildly uneven and totally wonderful.
Like most Southern European intellectuals, Corbucci was a marxist (at least sort of). Adorno, Marcuse and Foucault (among others) were read and discussed in artistic circles. There were high expectations that revolution was imminent. The Mexican revolution was the ideal setting for Corbucci's political westerns. There is little doubt that he wished to equate it to the situation back home, where a right-wing, fervent pro-American government surpressed any kind of revolutionary initiative. The Mercenary is still a hopeful, optimistic film, ending with Nero saving Musante's life, so he can fulfill his revolutionary mission.
'Compañeros' was made after it had become clear that the Paris student uprising of May '68 - considered by many to be a genuine revolution - had failed. All hope for a radical change was gone. Therefore 'Compañeros' is a more introspective, pessimistic movie, ending with Nero's suicidal attack, screaming the famous words, 'vamos a matar, compañeros'. As a result it also lacks The Mercenary's livelyness and brilliance.
Most of The Mercenary's flaws are due to Corbucci's lack of discipline and his need to fit in jokes. Of course there is that running gag with lightning matches on all kinds of surfaces, that is funny at first but becomes tiresome very soon. But Nero also shoots a plane out of the sky and brings down a horse by using his rifle as a blunt instrument. We see the revolutionaries dressed like angels - a complety silly device (yes, I know it's a disguise). In some scenes the body count is so high that they flirt with slapstick.
But what worried me most, was the fact that Palance's part is so ill-defined; he comes and goes in the movie, seems only to be introduced because he is needed for the film's most famous scene, the Arena. On the the other hand, his screen presence is - as usual - so strong that the film's main villain, Fajardo, is more or less eclipsed. All this make the film seem disjointed, almost arbitrary from time to time.
But still ...
Still, in my opinion, it is a true masterpiece of the genre. Many people would have preferred Milian in the part of Musante, but I think Musante's rather restrained performance provides a perfect counterweight for Nero's lovely mannered, laconic acting style. Moreover I simply adore his character: we see him evolve from a simple peon to a ruthless gang leader who develops a revolutionary ardour by the aid of the peasant girl who has started to love him. There is a very touching scene in which Musante, confronted with the map of Mexico, confesses that he never realized how big the country was. The scene is both simple and brilliant, and probably even more brilliant because it is so simple.
And who can ever forget that scene in the Arena?
Even if I rated 'The great silence' higher (currently no 3 in my Top 20), if I had to take one Corbucci to that proverbial Robinson Crosoe island, this could well be the one.