Complete Monster (includes Sonic Forces Chapter 2): Former terrorist and thrill killer Clyde the Jackal escapes from prison to become a ruthless crime boss. Killing his Arch-Enemy Stryker, Clyde takes the "Phantom Ruby" from the classic version of Eggman, before torturing both the past and present versions of Eggman for more information on the item. Mastering the Ruby's power, Clyde murders his own loyal henchmen before attacking Grand Metropolis, turning the world into Hell on Earth when Sonic and his companions fail to stop him. Psychologically and physically tormenting a jackal who tries to stop him, Clyde has several innocent wisps and their mother captured and transformed into brainwashed creatures to empower his own weapons. After he seemingly defeats Sonic, Clyde brainwashes the resistance group into maiming each other while leaving the survivors to be executed and, after truly being beaten, he tries to destroy the universe out of spite.
Claire: (rubbing her head) Ow! What was that for!?
Zero: WHAT DO YOU MEAN, WHAT WAS THAT FOR!? YOU KNOW EXACTLY WHAT THAT WAS FOR! WHAT THE HECK IS WRONG WITH YOU PEOPLE!
Scar: It was apart of your test!
Zero: AND YOU DIDN'T EVEN BOTHER TO WARN ME!? I COULD HAVE BEEN KILLED!
Claire: Will you calm down!?
Zero: AFTER I ALMOST GOT TURNED INTO A CHEWTOY, YOU EXPECT ME TO CALM DOWN!? I BARELY ESCAPED! I FELT MY LIFE WAS FLASHING BEFORE MY EYES, WHEN THOSE THINGS FIRST LOOKED AT ME! I HAD TO DO ALL THAT RUNNING, DODGING, AND JUMPING TO WALL TO WALL IN ORDER TO AVOID BEING TORN APART! MY LEGS GOT CAUGHT IN ONE OF THE WIRES! I MANAGED TO ESCAPE, BUT I GOT SCRATCHED IN THE PROCESS! AND LASTLY, I RAN AS FAST I COULD TO THE BLASTED DOOR THEN I HURRIED UP AND CLOSED IT BEHIND ME!
Ace: You were that scared?
Zero: NO, I WAS TERRIFIED! WHAT KIND OF IDIOTIC QUESTION IS THAT!?
Stryker: Zero, you need to calm yourself!
Zero: DIDN'T YOU HEAR ME SAY THAT I ALMOST GOT KILLED!?
Young Claire after burying her recently deceased mother:
Young Claire: I could… give up now, and just accept my fate. But I'll stay strong for you and for him.(wipes off the tears in her eyes) I love you, mother. I hope you and father get back together again in the afterlife.
Claire and Zero comparing Stryker to the moon:
Zero: The moon. It never ceases to be beautiful.
Claire: Yeah, I can see why people like too look at it.
Zero: The moon is vast, admired, and many consider it as something to look up to when you're feeling down. That was Stryker to me.
Zero's Nightmare Sequence of monsters dragging him away from an ignorant Axel.
The Lion's Den, the Horrific example of Initiation Ceremony. Robotic lions with lethal sharp claws... Wires strung and tangled throughout the room... Not to mention the lions getting triggered and ambushing Zero when he simply got hold of the cardboard key.
To begin, Zero's upbringing is tear-worthy. His father blamed him all on his mother's maternal death. No matter how much Zero tries to please him by robbing, he never lost his bitterness. So, Axel's mourning for Ellie's death can be considered a tear jerker too.
All of the Jackal Squad members' Dark and Troubled Pasts. Claire lost her father and mother at the age of 12. Brawn lost his adoptive father and most of his strength during his service in HAM. Radar, Ace, and Scar were raised in an unpleasant orphanage. Stryker's backstory is the saddest; he was a Child Soldier kicked out and left to die for surrendering.
Radar's guilt for not catching the fifth security guard, thus letting The Caper at the Silvertown Museum fail.
Stryker's death. Claire's reaction makes this worse.
Claire: Boss, c-come on! W-wake up!" she shakes stryker's body. "B-boss! Come on boss, enough fooling around! Boss! STRYKER! COME ON! WAKE UP! WAKE UP, DARN IT! BOSS! WAKE UP!" (is grabbed by Ace, cries on Ace's chest) He's unconscious! Tell me he's unconscious, ace. Tell me he's unconscious! Tell me!
Shadow the Hedgehog slaughtering all of the Jackal Squad but Zero, after the readers witnessed all of the pain and sweat the Jackal Squad and some of its members went through. Then Shadow coincidentally repeating Axel's abusive attitude in front of Zero. Man, so heartrending..
Spoilers for Memories of Infinite's Past and the Mid-Season Twist are unmarked.
Captain Obvious Reveal: The Phantom Terrorist is Clyde, who escaped that explosion years ago. However, considering the Terrorist's Complete Monster personality and the fact he commands a terrorist army, this is hardly a surprise to anyone who has read Memories of Infinite's past.
After Revealing himself as Clyde to Zero, the Phantom Terrorist delivers a "The Reason You Suck" Speech and proceeds to send him visions of his past memories reminding him of his biggest mistakes, just to outright shame Zero to the ground. Then he summons the Replicas of the deceased Jackal Squad and uses them to beat Zero nearly to death.
Clyde: Come now, Zero. We all know that you're weak. There's no point in trying to prove otherwise. So, swallow that pride of yours, and beg me to erase you.
The epilogue, though fortunately combined with Heartwarming Moments: Zero returns to the abandoned Jackal Squad's HQ and digs more graves for the fallen Jackal Squad and his father Axel. He demonstrates understanding of his father's hatred of him, that he lived a dreadful life under Clyde and lost the only person who loved him. He also asks Stryker for forgiveness of the disastrous decision that cost the Jackal Squad. Zero's visions of the Jackal Squad and him Riding into the Sunset nails it.