- C.C.'s description of the numerous ways Clovis killed her during her time in his captivity. And she had to experience all the resulting pain.
- Marianne has Mood-Swinger tendencies that even Charles can be notably unnerved by, especially when she expresses her desire for vengeance against V.V. for her first body's death.
- He also once couldn't eat for some time after accessing the memories of a particularly depraved noble. Lelouch makes a note to find out the name of said noble and avoid them.
- Desmond's Geass gives him the ability to alter the state of consciousness of everybody within an area he designates. This makes it very difficult to defend against his assassinations, since he can put his targets and everybody around them to sleep, then do what he came to do.
- C.C.'s threat to Desmond in Chapter 44 is pretty scary, even if her target is a scumbag. The fact that she makes it while using a whimsical tone — despite the coldly murderous air coming off her — really doesn't help. Even Milly, who's on her side and has every reason to hate the target of the threat, is noticeably unnerved.C.C.: Now, here's the thing, boy. I have been alive for seven centuries. Seven hundred years. No, I did not stutter there. In that time I have been both tortured and torturer and I know exactly how to break arrogant little peons like you; in fact it was a favourite hobby of mine for a decade or two before it started getting old. Your choice is to either undo the effect of your Geass, and earn a quick, painless death, or you can be obdurate, in which case I will take my time slowly breaking you and turning you into a bleeding, whimpering, mewling lump of bleeding, crippled flesh that I will not permit to die until I am satisfied that you know what pain and suffering really is.
- It's made clear that a Geass user suffering from Power Incontinence can be downright horrifying. One example is the Baroness of Gold Peak, who went insane when someone mowed the lawn and she wasn't able to turn off her plant empathy Geass. Another is Agent Sabenock, whose memory absorption Geass evolved into a Ward-type Geass, causing her to crack when she absorbed the memories of too many immoral people. She murdered several other Directorate personnel before finally being killed herself.
- Kadzuki wishes to reinstate kiri-sute gomen, with himself and his men as samurai...explanation
- Chapter 48 shows just how broken Suzaku is and it is horrifying. His Black and White Insanity has reached the point that his own subconscious realizes he is being childish and uses the voices of other people to try and convince him of this and Suzaku consciously rejects this.
- Melisande was willing to kill her own daughter to further her own ambitions. It's hard to blame Lelouch for having her shot by her Geassed servants in such a way that she bleeds out over an extended period, unable do anything to save herself, regaining the memory of what happened when Lelouch Geassed her, and that this is merciful compared to what he could have done to her.
Nightmare Fuel / Code Geass: The Prepared Rebellion