Tear Jerker / MacGyver (1985)

• "Black Rhino": Kate the conservationist had to perform a Mercy Kill on a poached rhino that is slowly bleeding to death. Her face is a mixture of sadness, anger, and sympathy. Mac, witnessing this scene, had this to say:
  MacGyver: That is the sickest, cruelest, most inhumane thing I've ever seen in my life.
• "The Kill Zone" has animals rapidly aging and dying due to a mysterious virus, and the scientist behind it accidentally contaminates herself and her dog with it, and MacGyver and Pete can only watch in horror as both rapidly age and die before their eyes.
• The episode "Humanity" is full of them. The plot revolves around Mac saving the life of a Romanian terrorist and trying to turn him to good. The terrorist's backstory is horrifying: He used to be a Child Soldier under Nicolae Ceaușescu. During training, he made friends with another boy, only for his commander to force him to kill the other boy. And then there's the ending. Normally, you'd expect the episode to end with the soldier escaping to the US and living happily. Not this time. He pulls a Taking You with Me against his evil commander, blowing them both up with a grenade. At the end all Mac can do is sadly honor the man for his selflessness. Pete notes that Mac helped the man discover his own humanity, if only for a little while, and that's no small thing.
• In "Twenty Questions," we see Lisa, the precocious, adorable teenage girl Mac befriended in a couple of previous episodes, dealing with a serious drinking problem (given that her parents are at least borderline emotionally abusive, and she quite possibly has unaddressed trauma from her previous adventures...) Throughout the episode, she's manipulated and, essentially, groomed by an older guy who befriends her, encourages her drinking, uses her to break into rich people's houses and steal from them, and then eventually sets her up to be murdered, with Mac saving her at the last minute. Thankfully, the guy goes to jail and it's implied that Mac will help her find a program to help her, but still...
• In "Flames End" Robert Englund, seriously Playing Against Type guest stars as a nuclear technician involved in a plot to steal atomic material but after having a crisis of conscience turns against the villain only to be shot and mortally wounded as a result. He lives long enough to help MacGyver avert a nuclear catastrophe, staring in horror at the instruments as his life ebbs away but giving a smile of relief as he sees the reactor begin to cool before finally dying.