SPOILERS!

[Swithin]

The protagonist of the film is shot and dies while attempting to do a good deed for and by the very person that he had previously had a run-in with earlier in the film.

It sounds a little like The Black Cat (1934), in which David Manners shoots Bela Lugosi at the end of the film. (Jacqueline Wells says to Manners: "He only wanted to help us.")

[Dargo]

The protagonist of the film is shot and dies while attempting to do a good deed for and by the very person that he had previously had a run-in with earlier in the film.

It sounds a little like The Black Cat (1934), in which David Manners shoots Bela Lugosi at the end of the film. (Jacqueline Wells says to Manners: "He only wanted to help us.")

Decent guess here Swithin, but the film in question would be about four decades newer than that one.

[Dargo]

The protagonist of the film is shot and dies while attempting to do a good deed for and by the very person that he had previously had a run-in with earlier in the film.

And now for another clue here:

The protagonist was a uniformed law enforcement officer.

[Dargo]

The protagonist of the film is shot and dies while attempting to do a good deed for and by the very person that he had previously had a run-in with earlier in the film.

And now for another clue here:

The protagonist was a uniformed law enforcement officer.

Next clue...and this one should give it away:

Said uniformed law enforcement officer is a motorcop

[EP Millstone]

The protagonist of the film is shot and dies while attempting to do a good deed for and by the very person that he had previously had a run-in with earlier in the film.

And now for another clue here:

The protagonist was a uniformed law enforcement officer.

Next clue...and this one should give it away:

Said uniformed law enforcement officer is a motorcop

Electra Glide in Blue, perchance?

[Dargo]

And now for another clue here:

The protagonist was a uniformed law enforcement officer.

Next clue...and this one should give it away:

Said uniformed law enforcement officer is a motorcop

Electra Glide in Blue, perchance?

Yep EPM, that's it. Good job. I knew the "motorcop" clue would do it.

(...you're up now)

[EP Millstone]

As one of the villains rapidly ages and dies, he watches his equally villainous rival floating down the river, singing a song from The Wizard of Oz.

[EP Millstone]

Well it took some googling, but Dr. Phibes Rises Again?

Correcto-mundo, skimpole!

The next round is yours!

[jamesjazzguitar]

After consistently missing the love of his life throughout the movie, a young man successfully hitchhikes.

Detour 1945 might work here; expect I don't know if I would define Tom Neal as a successful hitchhiker.

[KayFrancis]

After consistently missing the love of his life throughout the movie, a young man successfully hitchhikes.

Detour 1945 might work here; expect I don't know if I would define what Tom Neal as a successful hitchhiker.

LOL I was thinking of Detour too, but his experience was anything but successful lol

[Dargo]

After consistently missing the love of his life throughout the movie, a young man successfully hitchhikes.

'Five Easy Pisces' ?

Ahem, I mean 'Five Easy PIECES' ?

(...that first one up there of course being that now little remembered 1973 movie about a quintet of young ladies all born in the month of March and all of whom you might say are "of questionable virtue"...what, don't remember that one?...well, I SAID it was "little remembered" now days here, now didn't I?! ...yep, but then again, most of those movies they showed at the Pussycat Theater on Santa Monica Blvd back then ARE pretty much forgotten now days, aren't they!)

LOL

[EP Millstone]

After consistently missing the love of his life throughout the movie, a young man successfully hitchhikes.

"Whaddaya mean, it couldn't be me? I'm young . . . at heart!"