#1: Major Pa Tee Tint: Not only does he commit mass genocide on small Karen villages, but he also commits acts of molestation on young boys and uses women as sex slaves. So he takes the top spot without a doubt.
#2: The Martinez Brothers: They forcefully prostitute young women and sell them into sexual slavery. Definitely not as evil as Tint, but still up there.
#3: Col. Podovsky: If this man isn't a cold and calculating bad guy, I don't know who is. Podovsky (and Lt. Tay as well) kept plenty of POWs locked away and saw them as less than human, and even tortured Rambo for information.
#4: Col. Zaysen: I honestly find him the lamest Rambo villain, but as far as villainy goes, he doesn't do a whole lot of evil things, at least not on-screen. The only thing he does that truly counts as villainous is torturing Trautman for information.
#5. Sheriff Teasle: I honestly think that Teasle is the most complex actiob movie villain. He believes what he's doing is to protect his town, when really he's just another overzealous police officer. Overall, I would say he's the least evil villain in the series.