The thunder god didn't predict how Cassie's parents would go to extreme measures to rescue their daughter, and how Li Mei would go on a Roaring Rampage of Revenge after ordering her village to be destroyed.
Raiden also didn't anticipate Scorpion's defection, or that his lackeys (Shang Tsung, Noob, etc.) are planning to defect from him.
Vile Villain, Saccharine Show: While Mortal Kombat itself is a Crapsack World and isn't that saccharine, the fact that the Elder Gods fear Raiden more than they did with Shao Kahn or Shinnok did in the past (after he Came Back Wrong and is now an Omnicidal Maniac with sociopathictendencies) really shows how dangerous the deranged thunder god can be, considering that he's really close to pulling off a Class X-5 or Class Z Apocalypse How.
The War Room: While Raiden was meeting with his lackeys in chapter 52, Shang Tsung shows up, offering an alliance with the corrupted thunder god. Not only that, he also revived Mileena, Baraka, Mavado, Havik, Reiko, and Kobra.
Wham Episode: The prologue, where Raiden's invading Outworld.
Also during Cassie's chapter, when Cassie and Team S-F are horrified that Raiden will merge the realms just so he can "protect" Earthrealm from outside threats.
Chapter 52, when Mileena, Baraka, Mavado, Havik, Reiko, and Kobra show up alongside Shang Tsung.
Wham Line: When Scorpion announces that he'd rather work with an undead and brainwashed Quan Chi than a power-hungry Raiden in chapter 24.
Scorpion: I would prefer to work with the undead, brainwashed sorcerer than a Mad God lusting for power.
Wham Shot: You know you're evil when Hanzo bluntly states that he'd rather work for Quan Chi (albeit a brainwashed one) than Raiden. Cue Hanzo's Heel–Face Turn.
Also when Shang Tsung comes Back from the Dead and revives Mileena, Baraka, Mavado, Havik, Reiko, and Kobra.
What the Hell, Raiden: Kotal Kahn, Team S-F, the Lin Kuei, Liu Kang and Cassie Cage call out Raiden when he plans to merge Outworld and the Netherrealm with Earthrealm.
Kitana: "I have heard the pleas for help and explanations of the situation from all of you and after some consideration, we have come to a decision. It is clear by now that Raiden has gone insanefollowing his purification of the Jinsei, which resulted in his own corruption. He came here and stood before myself and Liu Kang and threw Shinnok's living head at our feet. He and the Shirai Ryu have invaded Outworld and will surely target the Netherrealm next. The only way to stop him is through victory in Mortal Kombat. And loath as I am to admit it, we must work together to achieve that victory."
We Used to Be Friends: Given what he did so far, all of Raiden's ex-allies (Fujin, Ashrah, Sub-Zero, Scorpion, Frost, Delia, Taven, Li Mei, Kai, Shujinko, Bo' Rai Cho, Team S-F, Jax, Jade, Kenshi, Sareena, Caro, Orin and the Cage Family) see him in nothing but contempt after he crosses the Moral Event Horizon by mass-zapping the Lin Kuei. Their sentiments about Raiden are shared by Liu Kang and the ex-revenants (Kitana, Kung Lao, Smoke, Nightwolf, Kabal, Stryker and Sindel), by Kotal Kahn and his warriors (Ermac/Jerrod, Reptile, Ferra/Torr, and Erron Black) and by others (Rain, Ruby, Sheeva, Kira, Darrius, Dairou).
Kotal and D'Vorah also qualify as this.
Dairou and Shujinko used to be friends with Hotaru.
Would Hurt a Child: In chapter 16, Raiden threatened to kill all the Edenian refugees in the camp, particularly women and children, if Ruby doesn't tell where Rain was.
Many of the Lin Kuei he either killed or maimed after crossing the Moral Event Horizon were in their early teens.
Pretty much a given, since he and Hotaru ordered the destruction of Li Mei's village with who knows how many children and women were killed.
Wouldn't Hurt a Child: Dairou feels that there is a line that he would never cross while working as a mercenary - hitting or killing a child. This is because his family, including his young daughter, were murdered.
Would Hit a Girl: Raiden and Kano kidnap and torture Cassie Cage to ensure Johnny or Sonya won't interfere in their plans.
You Are What You Hate: Raiden claims to "protect" Earthrealm, yet many of his ex-allies see him as a ruthless and cold-blooded megalomaniac no worse than Shao Kahn or Shinnok.
This is the whole gist of chapters 54 and 63, when Raiden's former allies berate him for what he's done so far.
You Have Failed Me: Kano and the Black Dragon are on thin ice with Raiden following the successful rescue of Cassie Cage by her mother and the two ex-Black Dragons.
You Monster!: Raiden, once he torpedoes through the line by mass-zapping the Lin Kuei and is responsible for Sub-Zero's comatose state. Cassie Cage, and later on, Kung Jin even call him an outright villain, referencing the Harvey Dent quote about paragon figures likeRaiden turning rogue.
You No Take Candle: Ferra seems to talk like this. The funny thing is that it verges on Hulk Speak for her when Torr is the Hulk of the duo.
Moral Event Horizon by mass-zapping the Lin Kuei. Their sentiments about Raiden are shared by Liu Kang and the ex-revenants (Kitana, Kung Lao, Smoke, Nightwolf, Kabal, Stryker and Sindel), by Kotal Kahn and his warriors (Ermac/Jerrod, Reptile, Ferra/Torr, and Erron Black) and by others (Rain, Ruby, Sheeva, Kira, Darrius, Dairou).