Anvilicious: Japanese universities tend to have high entrance standards compared to Western ones, and it's still not uncommon to find students struggling to get in. Knowing this makes the "getting a good score above all" thrust of the overly Elitist Volt hit a bit closer to home... Not that the lesson is a bad one.
Also, life, youth, and your humanity are important and can't be spurned or destroyed. Bias tries and ultimately fails to completely purge the four doctors of their humanity like he has done to himself, ruins others' lives for his goals, and is trying to create an artificial Fountain of Youth, meaning he abuses all three of these things.
Complete Monster: Great Professor Bias is the prime example of corrupters in the franchise. Having corrupted three geniuses before the show began, turning them into his students, Bias has them massacre the remaining geniuses at Academia. After kicking out Goh Omura and attempting to kill him, Bias recruits the aliens Guildos and Butchy. When Guildos tries to prove his superiority through Guild-zuno, it is revealed that both aliens are actually robots built by Bias to make the humans try harder, which he coldly tells Butchy to his face after Guildos's death. After Butchy is convinced to defect, Bias blows him up. Goh later realizes that Bias only wants his students for their brains, one of which will be used for the Giga Brain Wave, which will turn all humanity into Bias's slaves and make Bias immortal. After Yusuke saves the world from the Giga Brain Wave, Bias is reverted to a child who shifts his goals from conquest to destruction and mocks Megumi's kindness when she offers it before finally rejecting redemption.
Crowning Music of Awesome: "Taiketsu! Zunojuu" ("Duel! Brain Beast") is the quintessential 80's Sentai "Duel" theme. Strings and brass for the win.
The themes for the Bimotion Buster and Live Robo's Super Live Crash both have an assurance of victory about them. (In fact, if you've ever heard Bimotion Buster before, you're humming it now - you're welcome.)
The Mecha themes that start getting used after Live Boxer is introduced, and especially "Live Boxer's Song".
Magnificent Bastard: Great Professor Bias, who manipulated his students with Gash's help in order to initiate Mass Hypnosis and a Fountain of Youth. By the time this is revealed, he is cemented as The Unfettered, and even as his plans start breaking down, he's determined to continue, which ultimately leads to his death.
Moral Event Horizon: Bias is cold and egotistically heartless for the entire series, but there's just no coming back after it's revealed he gave Butchy memories of a happy life on Planet Chibuchi, only to tell him he's a robot, and those were programmed.
Then his whole Fountain of Youth/Mass Hypnosis plan is revealed, along with the revelation that he crossed the Horizon a looooooooooong time ago. Taking your students' brains and leaving the failures to die? Twelve times?
Never Live It Down: Megumi only cries in a handful of episodes, which somehow translates into her sobbing almost every episode.
Nightmare Retardant: Except for Bijuu Kemp, who looks completely ridiculous for a Sentai monster.
Rewatch Bonus: The final arc is so dark that fully appreciating it is hard to do with only one watch. Rewatching reveals certain tropes that can be missed due to the tragedy and evil that is prevalent throughout the arc.
Tear Jerker: Quite a few, given the dark nature of the last quarter of the show.
Arashi, after being 'dropped' by Bias, finally asks Omura what 8+4 is, a problem that's vexed him since his introduction. Upon getting the answer he notes that there's nothing left for him to do, remarks that it was a strange life, then straps on some dynamite and suicide tackles the as-yet unbeatable Brain Beast of the week.
All of the Volt members' final moments are like this. None of them are particularly easy to watch.