Badass Decay: Reese gets hit with this pretty hard towards the end of the series. For most of her appearances, she's a competent warrior and a constant threat with her piloting skills and Manipulative Bitch schemes. However, once Hiltz disposes of her and she starts traveling with Raven, she's demoted to a sideline position where she can't do anything for the final episodes other than cry and scream Raven's name.
Ask anybody familiar with this series, odds are they'll treat the post-Time Skip episodes as a Sequel Series with the subtitle "Guardian Force", in the same vein as Naruto Shippuden or Dragon Ball Z. The post-Time Skip episodes are in fact, just the latter half of Chaotic Century.
If they're not treated as two separate series, the pre- and post-Time Skip episodes will probably be referred to as "Season 1" and "Season 2", respectively. There was no break in the episodes when they originally aired, the Time Skip is just the start of a new story arc.
Gunther Prozen, the Evil Chancellor of the Guylos Empire, keeps a pointless war with the Helic Republic going so that he can seize control of the Empire. Attempting to murder the child emperor Rudolph, Prozen sends his personal killer, a boy he indoctrinated from childhood named Raven, after him while also sending "rescue squads" that he has Raven destroy in order to cover himself while he continues the war. Prozen then attempts to awaken the ancient weapon the Death Saurer and demonstrates its power by attacking his own capital. Even after defeat, Prozen adopts the identity of the Dark Kaiser with intention of re-awakening the Death Saurer and wiping out organic life.
Hiltz is an Ancient Zoidian who desires to exterminate all human life and rule Planet Zi himself. Initiating a series of terrorist attacks to destabilize the hard-won peace, Hiltz kills any men who fail him and even tries to kill his right-hand woman, another Ancient Zoidian named Reese, just because she's no longer useful to him. Revealing his secret weapon the Death Stinger, Hiltz proceeds to bombard civilian targets and announces that when he proceeds to the Guylos Empire, he'll destroy every civilian town and city he sees along the way. Finally fusing with the Death Saurer, the sadistic Hiltz dedicates himself to exterminating all organic life on Zi, gloating how he will be the one to rule over everything.
Draco in Leather Pants: Raven is an egomaniacal bloodthirsty killer who starts off as Prozen's attack dog, and later goes rogue and becomes a terrorist. He abuses and belittles Shadow, wants to commit genocide against all Zoids, and will even murder his own allies; yet we're meant to feel sorry for this jerk because he has a tragic backstory. Predictably, he has tons of fangirls.
Epileptic Trees: Fans have speculated that an uncut dub for this series (as well as New Century/Zero) exists in some capacity considering some of the slip-ups of swearing and blood occurring during it's American broadcast. Since the series has been absent from American shores for many years now, this may never be known. On the other hand, this is averted with the Latin American Spanish dub, since it was dubbed from the original Japanese version, albeit according with some sources, it was dubbed without taking into consideration ShoPro's American branch rights over the whole region, including Latin America.
The true Death Saurer itself. Once it fuses with the core of the Death Stinger and Hiltz has control of it, it's nigh-unstoppable. The combined forces of the Empire and the Republic do no damage to it whatsoever. It even gains the ability to split its Charged Particle Beam, enabling it to simultaneously hit multiples across the entire planet with ease.
When Irvine's Command Wolf bites the dust after being hit by Raven's claw attack. More specifically, the monologue that Irvine delivers to the dying Zoid is what pulls the heartstrings.
Then there's the strained response that the Command Wolf delivers to the above mentioned monologue.
As if that wasn't enough, when Irvine is given a "Reason You Suck" Speech by Moonbay, the Command Wolf chimes in and basically tells him to go through with it.
Rudolph's blood-curdling scream when Van's Shield Liger gets destroyed.
The death of Shadow. Raven's breakdown after shows that he really did care about his Organoid. Shadow was the only family he had left and now he's gone.
When Fiona vanishes from Vans arms after taking a nasty hit that looked like it mortally wounded her, you can't help but hear the strain in Vans voice as he cries out for her, believing that she had just died. If not for the fact that Zeke knew were she went, it's likely Van would've gone on a Roaring Rampage of Revenge to finally put an end to Hiltz