The exchange of Breaking Lectures between Optimus and Megatron when they meet each other again for the first time in the show is simply awesome as they both get under each other's skin.
Optimus: You're still ruled by emotions. That's not very technologically "pure", is it? You can feel the anger rising inside you! You're just about ready to explode! {This gets Megatron to go into Beast Mode} Look at yourself, Megatron! See that thing that you despise the most! Cybertron will never be pure as long as the beast exists within you! You failed.
Megatron: No, Primal, you have failed. You're still too late to save your people. Billions of Transformers, their extinguished sparks are on your hands! Perhaps if you had won the Beast Wars, things would be different. Who's to say? {This makes Optimus angry and revert to Beast Mode}Who's the beast now, Primal?
Megatron's actions in "The Weak Component" have always seemed his highlight as a character. Crippled and isolated, his army disabled, Megatron is on the verge of defeat by the Maximals...but he uses their divisions against them, to recruit Rattrap for one night and to buy time to regain his strength. And in the end, once he could destroy the Maximals, he doesn't... not so much for honor as because he made a bet, he lost, and he always did enjoy gambling. It really highlights BW Megatron at his charismatic, plotting, gambling, megalomaniac best.
He calls Rattrap's bluff to call in the Maximals immediately with a grin, noting a very obvious reason why.
Megatron:You wouldn't be here, unless you had nowhere else to turn. So let's cut through the signal noise, shall we?
In the Season 1 finale "End of the Line," Rhinox has just blasted Optimus Primal with the Key to Vector Sigma (which will wipe out any organic material inside him and eventually drive him offline) and is ready to do the same to Megatron. It all seems like a total victory for him... until he suffers a malfunction and is quickly locked in place via power-nullifying energy rings. Megatron laughs and reveals that he had made sure Tankor/Rhinox would be unable to destroy him via hardwiring it into his programming, and thanks to Rhinox working against him, Megatron now has the means to exterminate all organic life on Cybertron. If Optimus hadn't activated the Plasma Energy Chamber (which keep in mind, would destroy all technological life on Cybertron and would lead to its temporary annihilation in the next episode), Megs would have won right there. This moment shows how brilliant Megatron truly is, even using the treachery of others to achieve his goals.
Megatron: Mwahaha! You can't destroy me! It's hardwired into your programming![turns back from his dragon to his normal self inside his command harness] Did you think I would grant you a spark, and then not protect myself from your treachery? You've been a perfect pawn all along, your independent mind weaving webs of deceit I would never have conceived. I must thank you: if I'd never let you roam free, I never would have obtained the key to my victory!!
Everything Optimus does in "Fallout." After pulling a massive What the Hell, Hero? and unleashing the Plasma Energy against the Key to Vector Sigma, the clash of energies destroys his physical form, with Cybertron about to follow. The Allspark itself calls him out on it, and Optimus realizes what his actions will lead to. After a little help from the Allspark and Rhinox (and presumably a massive amount of sheer willpower,) his body regenerates. He proceeds to use himself power conduit, taking advantage of his technoorganic body by channeling both the energies through himself and back into their respective sources and into the Oracle before being blasted into atoms. The Allspark itself is impressed, and offers to let him join the Matrix, but Optimus opts to finish his mission, upon which The Oracle recreates his body. Like a boss, Monkey.
A lot needs to be said about Thrust. He was a Vehicon general from the very beginning to the very end, outlasting Jetstorm and Tankor and even the more advanced Obsidian and Strika, and is virtually unafraid to speak his mind about anything, to the point where he outright chews out Megatron to his face about him using Maximal sparks to power his generals. All of this is even more of a stroke of awesome when you remember whose spark he has. It's Waspinator, who also survived the Beast Wars.
Obsidian and Strika's introduction to the show's dynamic. Initially seeming to be trigger-happy, single-minded drones that can only shout their transformation code-word, they start out trying to perform giddy hit-and-run tactics, with the Maximals chasing them over to a bridge. It's then that Primal realizes that something is amiss, and that they weren't chasing the generals; they were being corralled by them as an army of Vehicons descends upon them. Strika and Obsidian proceed to move in, showcasing that they are in fact master tacticians at heart, and were preying on the Maximals expectations after dealing with Tankor and Jetstorm.
Obsidian: Although he took his name from a great leader, Optimus Primal never learned the first rule of warfare: never underestimate your opponent.
Strika: "Terminate?" "Obliterate?" Can you believe they fell for that?
Megatron still being able to hold his own against the Maximals despite being in the Diagnostic Drone! Word of God has stated that was intentional due to a speech that says he's badass no matter what form he's in.
In the second to last episode where Cheetor is the only Maximal left functioning and is exhausted, weakened and beaten, and then takes out Thrust, Obsidian and Strika by himself. First by sending Obsidian and Strika into space and then going one on one with Thrust. During a final struggle, he grabs one of the spark extractors and then rips out Thrust's spark.
The final episode is just one big Awesome Moment with the Optimus Primal vs Optimal Optimus body Megatron fight, as Optimus manages to serve as a Curb Stomp Cushion against his previous form despite being significantly outgunned. It culminates in Optimus sacrificing himself to destroy Megatron (Megatron's giant facial expressions of fear are incredible!) and to reformat Cybertron. This also includes the epic aerial battle over and under the city leading up to that, lasting almost an entire episode by itself!
