In the first episode, we see the kids run from an eerie looking surveillance robot. The robot is huge, tower-shaped, and has a big eye in the center. And it projects it's beams at a group of small children.
The complete downfall of Earth at the hands of the Zaal Empire. Unlike Combattler V, Voltes V, and Daimos where their respective Earths remain strong and standing in face of Alien Invasion, this Earth fell to Zaal's might and is reduced to surviving pockets of human stragglers who have to struggle to manage their remaining resources, and the cities and towns of Earth are in ruins, with Robeasts stationed on the planet to deter any rebellion against them.
The horrific treatment of the clones is this, as they were made only for the purpose of ensuring there is no Succession Crisis of the royal family in the Helios Empire. When a royal suffers an injury, the clone gets tortured to have that same injury as well. But when a royal is critically injured, the clone is killed so that their organs will be harvested and implanted in a surgery. And when the emperor dies, his clone takes his place to continue the charade. Even then, the clone would end up terminated eventually once he outlived his usefulness. Rinse and repeat. It's a never ending cycle. It's no surprise that Dolmen had finally snapped and created the Zaal Empire to wipe out the Helios Empire and then conquer the universe.
Dolmen's transformation in the Grand Finale. He starts out looking like the noble Emperor Palmillion, and then he gets hit by the UV rays, which causes him to slowly deform into a monster. His skin starts wrinkling as it turns from pale to blue, his brown hair turns golden and expands in volume, and his sclerae turn deep purple. The man looks nothing like he did before, and this whole sequence is somehow less disturbing than his eventual One-Winged Angel form.
Kento being Driven to Suicide in episode 26. He hears his mother's, his sister's and Sanae's voices telling him to pull the trigger on his head. Considering that he's 15 and already forced to shoulder the burden of saving the Earth, there's a chance he might have actually done it as he felt like a huge failure.
