At first, the operations in Under the Knife / Second Opinion are relatively low-tension operations: removing glass from a patient's arm, removing tumors from another patient's stomach, burning away polyps from someone's throat. Might make some players quesy, but nothing really life-threatening happening. However, the fourth operation is a Wham Episode, giving you the first life-or-death operation in the game. Defibrilator, done. Remove glass shards from patient's chest area, done. Open up patient and oh god there are shards of glass in his heart too!
Just take a moment to think about what GUILT and Stigma do to those they infect. That is what could happen if someone bio-engineers a disease.
Trauma Team has a pretty scary one. The Rosalia Virus causes WAY too many people to die. And when a person truly dies, they bleed to DEATH through anything with a hole, including their EYES.
Rosalia is filoviridae (Ebola-type virus) that is spread by butterflies, or more accurately, the wing scales they shed during their migration period. While giving you a touch of Ax-Crazy provided it spreads to the brain. It also just happens to leave it's trademark black bruises in the shape of a freaking CLAW on the liver of most victims. It's likely a consequence of the bruises forming near the entry point of the liver but it still looks frighting as all hell.
By Under the Knife 2, Neo GUILT also causes Ax Craziness.
Call it Narm if you must, but Neo-GUILT-infected Adel demonstrates a rather cruel use for the Healing Touch: Using its Bullet Time properties to kill people.
"Dr. Stiiiiiiiiiiiiiiles...do you know what else the "Healing" Touch is good for? It's also good for...KILLING◊!"
In earlier operations, if you fail an operation, another doctor will simply take over for you, securing the patient's life. However, in later operations, whoever you're playing as is often the only doctor capable of dealing with whatever is inside the patient, which means if your patient's vitals hit 0 (or you run out of time), your patient will outright die.
In Under the Knife 2's final operation, the Big Bad has rigged the room to infect everyone inside with Neo-GUILT if she dies. Oh, and she has to be operated on, because she is infected with Aletheia. And the operation has several ways of knocking out a large fraction of her vitals or outright killing her if you make certain mistakes. Good luck.
The final Episode of Under the Knife (not Second Opinion) reveals that GUILT is cultivated inside seven different children, all of which are labeled as "Sinners"; Adam's implication is that they are guilty of some sort of sin bad enough to deserve this fate. No wonder the Big Bad is filed under Complete Monster in the YMMV tab. In Under the Knife 2, we find out that such biological atrocities run in the family: Heinrich does the same with his own children.
In Trauma Team, Tomoe's mission Resolution is rather creepy: you guide her endoscope through a shifting maze of collapsed rubble with only the desperate cries for help from those trapped within to guide you. Pretty frickin' unsettling.
Another one in Trauma Team, At the end of one of Naomi's missions a bomb (inside a teddy bear) that is supposed to kill Naomi is taken by Alissa and EXPLODES WHILE SHE'S HOLDING IT. Even though it was supposed to kill Naomi, it killed Alissa's parents and almost killed Alissa, leaving her orphaned, so in a really bad way, the Raging Bomber still wins, by killing even more people then she wanted. Although it makes it more satisfying once you catch her.