Most brutal kills ever put on screen

Well, right off the top of my head, there's Private Mellish and Medic Wade in Saving Private Ryan. Both their deaths were far more upsetting than the couple in Zodiac. You had really gotten to know both of them. They weren't anonymous like the Zodiac couple. With Mellish, you have the guy who has been the comic relief of the film up to that point getting slowly stabbed to death by a hulking German who has him completely overpowered, and who is whispering to him to just let go, it'll be easier, etc. while he sloowwwwlly eaaasses the knife between Mellish's ribs. With Wade, it's this gentle, meek guy who you heard talking about his mom a few minutes before choking on his own blood while he tries to tell the others what to do to help him. You don't see him actually getting shot, but his death scene is excruciating. You know there's nothing that can be done to save him, and he, with his medical training, knows it too.

There's an old 1970s African Adventure movie set in WW1 called "Shout At The Devil" that has one of the most horrifying deaths ever, and you really don't see much of it, but it is devastating. Roger Moore has married the daughter of his ivory poaching partner, Lee Marvin. The happy couple has a cute little baby girl. We see how Moore and his wife and even Lee Marvin love the baby very much. One night, Native Askaris employed by the Germans attack the farm they live on while Moore and Marvin are away. The Aksaris throw the baby alive into a burning building. Up to that point, the movie had been verging on being a buddy-comedy about Moore and Marvin's hijinks. Then a baby we've gotten to know gets roasted alive.

The scene in "Henry: Portrait of a Serial Killer" when Henry and his pal Otis kill an entire family, kids and all, in their home after torturing and humiliating them makes the Zodiac scene look like a Disney movie. I bought the DVD of it, watched it once and then sold it. I never want to see that scene again.

I'm sure there are others I could name, but I'd have to think on it. The couple at the lake in Zodiac died unpleasantly, (well, the woman did, as the man survived) but we had no real emotional investment in them and the scene was over very quickly.