In the second trial (spoilers): The victim was suffocated with a cushion and the culprit initially seems to be drowned, but before they do, they’re killed in an explosion.
Daiki’s father is heavily implied if not confirmed to be abusive. Haruka, who put her own child into a killing game back in PINK, returns and claims to not be a mother.
Also, Hideyuki/Matthias (who is 17) has spent a few years as a human trafficking victim. Nanae was forced into an arranged marriage and has a daughter but the relationship was with someone her age.
Atsushi has his eyes damaged after threatening Monomoko, causing his sprite’s eyes to briefly go red. There is no visible lasting damage but they seem to be in pain for a little while after and there are lingering effects on his vision. Noriko wears an eyepatch but it seems to be decorative.
Everyone was drugged unconscious for abduction at some point or another. In the first trial, after the culprit reveal, Nanae knocks Daiki out (causing some pretty bad damage as later shown) and is soon knocked out in self-defence by Mion. The second victim was drugged unconscious before death.
Atsushi briefly chokes Daiki in the first investigation for pushing his buttons one too many times at the wrong time. It doesn’t lead to permanent injury.
In episode 65, [Phobia Game], the character Akiba Taku chooses to take a punishment that makes him cough up blood (Not sure if that counts but it triggered me a bit so I still wanted to list it) Afterwards, he says he thinks he's gonna vomit and 2 other characters take him over to a trashcan. Nothing actually happens and the coughing up blood isn't visually seen, only audio. In episode 172, [Nosocomial Phobia], Shishikura Osamu vomits as soon as the episode starts. It lasts for the first 6 seconds and its only audio but the audio sounds very realistic and triggered me. I suggest you just mute whatever your using before you open the episode if you don't want to hear it. In episode 195, [Mafia-Marked Man Vendetta: Medical Bay] Sou and Maekawa enter the medical bay and Maekawa notes how it smells bad because multiple people had vomited in that room the day before. Sou then investigates the trashcan, which has papers covered in vomit and starts searching through them. Maekawa sounds like she's gonna vomit out of disgust, but nothing happens. Maekawa describes how the paper is "soaked." If this triggers you, I think you can skip the episode without missing out on much of what happens. In other episodes (not exactly sure which ones because there's a handful) the characters say that their gonna vomit as a joke or out of disgust or shock, but nothing actually happens. Episode 172 is the only time anyone actually vomits so far (unless you count episode 65 too) so you don't have to worry too much (my bad if I missed anything)
Technically the whole series given it’s set in a scientific facility, but specifically when Shingo performs checkups on other characters and when he and Mion discover a surgery room in the second chapter.
Erina makes an offhanded remark upon finding out that Sou is blind asking if that’s why he dresses like a girl, but after he says this is just how he likes to dress, she drops it. It isn’t played as a good/funny thing.