Anti-Climax Boss: Zorax was built up as a mysterious leader of the Sark Cult, brainwashing Zemerik and creating an entire force for his mysterious goals. It's revealed that he works for the Karmordians and... Zemerik swiftly hits him in the back with his electric whip and destroys him after being freed of the brainwashing.
Complete Monster: Krytus, from season 2, was known as the most malicious being in the multiverse. Ambitious and power-hungry, he restarted an eons old war between the Red and Blue Sentients to conquer the multiverse. When his own twin sister, Sage, froze the Red Sentients in stasis, he retaliated by carrying out a genocide on the Blues. It was also revealed that he had several thousand Blue Sentients tortured to death, and the one who managed to enter hibernation to escape him was punished by having his body sabotaged, dooming him when he woke up. After being freed from his prison, he then throws the one who released him off a cliff. He then spends most of the series trying to kill Sage. After being forced into an Enemy Mine with Vert to escape the Shadow Zone, he sets up an ambush for Vert the moment they're out of it. Not even the other villains are safe from his wrath, as he starts an Enemy Civil War among the Vandals through Grimian. In the season finale, when he and Sage finally have a confrontation, he asks Sage if it was worth it to imprison the Red Sentients, in which she replies that if she hadn't, Krytus would've endangered not only the Blue Sentients, but the multiverse. Krytus actually agrees with her as he plans on using them as an army to conquer the Multiverse itself and cares nothing for them.
"Funny Aneurysm" Moment: Indy Car driver Dan Wheldon appeared As Himself in "Full Throttle" and spends the whole episode violently crashing. Not even a year after the episode aired, Wheldon was killed in a violent crash at the IZOD Indy Car World Championship
Moral Event Horizon: If he hadn't crossed it before then, Krytus crosses this in "Unite and Strike" by admitting Sage was in the right by freezing the Red Sentient Civilization in order to stop him and not caring, showing that he knows full well that what an evil, terrible person he is and doesn't care.
The Ancient Ones haven't been seen yet, but what was seen of them is rather...unsettling...
A little flashback to season one, but does anyone find it creepy on Sage's "Human Friendly" Joke? If you think of it, she made it all too real and not to mention her laugh.
Tear Jerker: In Unite and Strike, Sage was "killed" by Kyburi, she uploaded her memory to the Battle Force 5 vehicles and quoted the arc concept from the first episode and Title Drop before "dying". As she faded in Vert's arms, Vert thought he has failed his mission, almost gone berserk to the point he got only revenge in his mind. The plot was classically executed; as Vert is the leader of the team, holding almost all the responsibility, and previous episodes keep remind the viewers about it. When there's a moment where he thought his plan has failed, seeing Vert at a brink of Heroic B.S.O.D. is almost unbearable.
Villain Decay: Zemerik to some degree in season 2. Justified due to the arrival of Krytus, who takes over the Sark and robs him of his army. Not to mention the fact Krytus is much more powerful than he is. This is, however, largely averted with the other villains, as they remain pretty much a consistant threat throughout. Kalus even Took a Level in Badass in season 2 and became an even match for Krytus in combat. The Red Sentients do become easier to deal with, but that's largely due to the Battle Force 5 learning to deal with them and getting the Fuser upgrade, and they still remain the most dangerous villain faction.