The dog doesn't explicitly die, but he goes missing and isn't seen again for the remainder of the film. His fate is unknown, but if you truly care about the safety of dogs in movies, it's likely it will upset you to an extent.
Many references but not generally shown in detail - LSD, acid, weed (shown but briefly) and many characters are shown as high which contributes to violent or strange behaviour.
An ox was hacked to death during a religious ritual. As far as I can tell the ritual would have happened anyway so it wasn’t killed specifically for the film
There are many amputated heads shown and the colonel says the reason that he is insane is because he saw children getting vaccinated by soldiers for polio but because those kids where in an indigenous tribe the parents cut all of their arms off thinking the soldiers did something bad to them, the colonel saw the pile of little arms. This is talked about but not shown
While it’s not specifically stated, you can see the mental deterioration of soldiers and them doing things which many people would consider war crimes or inhumane. It’s a pretty good take on what war can do on the human physique.
No direct suicides are depicted onscreen, but late in the film a major character does not protest, fight back, or run away when he knows someone is going to kill him.
slurs used by american soldiers against Vietnamese, "gook" "slope" also an african american soldier uses the word n***a in reference to an unseen enemy
There are other deaths shown before mostly of Vietnamese people or unnamed soldiers but the first two main named characters to die are **kind of spoilers** both black men.