Spoilers for the ending. Godzilla's head is exploded with a bomb and there are scenes where the top of his head, everything above the mandible, is gone.
Godzilla also steps on and tail smashes a lot of people, so their heads got squashed with the rest of them.
During the destruction of Ginza, we see a building that a news team is standing on top of crumble to the ground. It can be assumed that they do not survive.
A major character seems to die partway through, and a significant portion of the movie is devoted to showing other characters realistically respond to and grieve over their death, but they are eventually shown to be alive.
There is a newscast that mentions 30,000 casualties in Godzilla's attack. Many deaths are offscreen but Godzilla is shown stomping and biting several people to death. His "heat ray" also destroys ships and tanks.
There are three characters whose parents are mentioned early on to have died from air raids.
Later on a girl's adoptive mother seems to die from Godzilla's attack on Ginza, and her father states his intent to sacrifice his life to kill Godzilla. Though he ultimately ejects from his plane at the last minute and survives, and the ending reveals that the mother's survived as well.
There is one scene where the main character suddenly covers his mouth, which made me nervous, but it turns out he’s just trying to silence the sound of his breathing! The film is safe for fellow emetophobes!
It takes place in the mid-1940s, so obviously 9/11 doesn't occur. However, we do see several large buildings crumble and widespread city destruction, so be aware if that imagery is triggering.
The film’s ending takes place in a hospital. While nothing tragic happens, it’s still emotional, as it involves the main character finding out someone he loves is okay.
There are multiple instances where the main character is so overwhelmed by fear/horror he completely shuts down and freezes. There is also an instance where he believes he may not even be alive and his whole life since the end of the war is just a hallucination.
Due to war and Godzilla PTSD, the main character has a meltdown where he can't tell if he is actually still alive or just the dreams of his dying self. He is left crying and panicking.
The main character has a few. During the island scene early on, he freezes during the first Godzilla attack. He is shown hyperventilating and totally unable to react.
Mostly booming noises, but rarely are they especially jarring or jump-worthy. English subtitles are paraphrased from memory, and some notes are kept as vague as possible to avoid spoilers. Timer starts at this first sudden noise: The alarm sounds on the beach at nighttime, then Godzilla appears somewhat suddenly. 0h22m: Kōichi wakes up crying and says, "Am I even alive? Is this real?!" Then a loud transition. 0h34m: Boat crew see dead fish, they have a longish conversation, after someone says, "Somebody's gotta do it," expect a noise. 0h37m: Godzilla stands up, and right as he's about to roar he's hit with an explosive. 0h48h: On the boat, then sudden splash. 0h49m: Announcement says, "Evacuate, this is not a hoax," then sudden cut to chaos. 0h57m: After devastation, Godzilla lets out a roar that could be startling. 1h07m: Men look out the window, someone flips a switch and then... 1h32m: They're on the ship getting ready, then sirens, then a booming sound. 1h44m: Really quiet, then after someone says, "Did we get him?" there's a rumble. Otherwise, expect a few other moments during the climax (which my friend didn't write down) where a loud noise is preceded by brief silence.