Yes, this is the one that takes place in Afghanistan. I'll agree that this is the worst Rambo movie out of the four, yet it is still totally incredible.
The movie starts out full throttle with John Rambo stick-fighting for cash in Thailand. He's giving his earnings to and helping construct a temple. Very noble of him. He shows more of his sentimental side in this film. After declining to help his father-like figure with a mission, Col. Trautman is captured. Rambo is compelled to rescue him. The objective was to help arm the Afghanis against the Soviets. (See Charlie Wilson's War for a comical, feel-good cliff's notes on this serious part of the U.S.'s meddling history).
The torture that Trautman endures while captured is weak (especially compared to Rambo's past POW abuse or anything shown on the torture approving tv show 24) but the one-liners area great. Only two Mujahideen, one a young boy, aren't afraid to help with his suicide heroics. Their first rescue attempt fails but the second is a success. Rambo sustains a puncture wound that he ridiculously cauterizes all the way through with gunpowder. Lots of explosions, bloodshed, and savagery earned this movie the Guinness Book of World Records title for most violent film ever. Rambo(2008) would go on to trump the body count of this blood-spattered treasure.
John Rambo is so unyielding that he kills his adversaries twice. One is hanged after a grenade pin in his jacket is pulled, blowing him to bits (similar to Rambo [IV] when a villian is blown up on a landmine after getting hit with an arrow). In the final action sequence, the head Rusky is shot to pieces in a helicopter right before he loses a game of chicken with a tank-driving Rambo and then exploding. Surprise!, Rambo makes it out alive.
Before the credits roll there is a sweet dedication to the "gallant people of Afghanistan."
Thanks to Defensive Listening from Weshotjr for contributing some useful facts about this movie.