This is how Diesel overthrows Trixie and tries to kill her in Unicron Returns.
[We view the villains' base close up. Trixie trots back and forth, wondering where Diesel is]
Trixie: [groans] Where the heck is Diesel?
Aria Blaze: Yeah! What's taking him so long?
Sunset Shimmer: I think the good guys killed him.
Sonata Dusk: [gasps] [glares at Adagio] This wouldn't have happened if Unicron hadn't placed that crystal on you and you hadn't disbanded us in the first place, Adagio!
Adagio Dazzle: Look, Sonata, I apologized and we rebanded, okay?! And we shall remain together, as always before I was consumed by the Anger Crystal and disbanded us.
Sunset Shimmer: [growls] Will you quit it with the arguing?! [sighs] Right now we've got bigger problems. Diesel is missing and you argue about it just because of some crystal that Adagio was possessed by? How much bigger can problems like this get.
Adagio Dazzle: Look, guys, I was wrong to disband the Dazzlings. But from now on, we will stay together.
[The other girls and Trixie turn away from Adagio and continue with what they are doing. Adagio suddenly evilly grins]
Adagio Dazzle: [to herself] For now at least.
[Adagio removes her hand from her forehead to reveal an Anger Crystal shard on it. Diesel suddenly enters the room]
Diesel: [in Unicron's voice] Hello, girls.
[the girls turn and gasp]
Sunset Shimmer: Diesel? But we thought you were killed.
Diesel: Oh, no, dear Sunset. I am the Chaos Bringer. I am... UNICRON!!!!!!!!!
[the girls gasp upon hearing this. Diesel's eyes glow purple]
Adagio Dazzle: Diesel! What has gotten into you?
Diesel: [transforms into a robot] Unicron! That is what has gotten into me!
[Diesel throws Trixie aside and takes out his sword as he corners the Dazzlings]
Sonata Dusk: Adagio, do you really think he is trying to...
Adagio Dazzle: ...Kill us with that thing.
[Diesel's purple eyes glow brighter]
Adagio Dazzle: Well, it seems that way!
Sunset Shimmer: [sees what's happening and takes out her Luger] Diesel! Stop! [shoots at him]
[The bullet hits Diesel in the arm and Diesel turns away from the Dazzlings, knocks Sunset out and goes after Trixie, who is lying on the ground unconscious]
Diesel: Remember this day, my dear Trixie. [raises his sword] THAT YOU MET YOUR DISMISS!!!!!
Thomas: Diesel! Stop! [puffs up to him] You have to fight against Unicron. Please.
[Diesel puts his hands on his head, screaming in pain]
Diesel: Argh! Stop me!
Thomas: How? What should I do?
Diesel: Please, Thomas!
[Thomas transforms and he and Diesel fight. Diesel then takes out his sword and hits Thomas with it, sending him flying]
Thomas: [tries to transform but can't] [grunts] I c-can't transform!
Diesel: [as Unicron] I'm afraid the Dark Energon within this sword makes that impossible. [raises his sword once more]
[a sudden blast in the back stops Diesel and he turns to see Percy, James and the rest of the Steam Team, all in their robot forms, standing behind him]
Twilight Sparkle: Nopony does that to my tank engine! Nopony!
[Henry attempts to slice Diesel in half with his buzz saw in an attempt to free him from Unicron. However, Unicron makes Diesel fight against him and he throws Henry to the ground]
James: You won't get away with this! [charges at Unicron]
Diesel: You don't stand a chance! [aims the Immobiliser and fires]
[Waves from the Immobiliser hit James, immobilising him]
[the Steam Team, including Henry, charge at Diesel, raising their weapons and letting out a battle cry. However, Diesel aims the Immobiliser and freezes them as well. He finally manages to freeze Thomas as well]
Thomas: [grunts] I can't move!
Rarity: [grunts] None of us can!
Diesel: [cackles] No one, can stop me! NO ONE!!
[then something blows up his immobiliser ray]
[Diesel turns to see Zorran and the Zed Stacks standing behind him, all with weapons in hand]
Diesel: Zorran? Zug? Zip? Zak? Zebedee?
Zorran: ZED STACKS, FIRE!!!!!!
[the Z tugs fire all their weapons at once. Several bullets hit Diesel but he repels them and fires at them too]
[but since the Z-stacks blew up the immoblizer, our heroes at now moving again]
Percy: Now to disable this diesel. [he shoots one of his grapling hooks which spins around Diesel's legs]
Pinkie: Hey Diesel!
Pinkie: You wanna hear a knock-knock joke?
Diesel: Not really, but go on.
Diesel: Who's there?
Diesel: Slip who?
Percy: Slip and fall! [jerks the hook's cable sending Diesel falling to the ground]
Diesel: [as Unicron] Why, you little!
Pinkie: Ha-ha! Fooled you!
Percy: Can you transform now, Thomas?
Thomas: I will try, Percy! [transforms] I can!
Thomas: [turns back into a robot] Now it's time to rid Diesel of Unicron!
[Thomas tries to hit Diesel but Diesel frees his legs and throws Percy aside]
Diesel: [cackles] You have outnumbered me for the last time! [raises his sword and is about to take the killing blow when it is blocked by Thomas]
Thomas: No one does that to my friend! NO ONE!!!!!
Ratchet: Kick him in the tail pipes, Thomas!
Sweetie Belle: Give him the puncher! Smack him!
[Thomas throws Diesel to the ground and takes out his Iron Blaster but Diesel repels his attack and takes out his sword, Thomas doing the same and the two dual]
[Meanwhile, Knock Out is battling a few Vehicons. One of them scratches his paint and he slices it in half]
Knock Out: You scratch my paint, I scratch yours!
[He then transforms into his automobile and races off]
[Outside the villains base, Thomas and Diesel are still fighting]
Thomas: You won't win, Unicron!
Diesel: Oh really?
[a sudden purple light extends out of Diesel's Spark at the top of his head and a large purple tornado appears behind him. A huge wind begins to blow as Diesel is lifted into the air]
Diesel: Remember this day Sodor that I extinguished OpThomas' Spark! [aims a beam of Dark Energon at Thomas and it begins draining him of the Matrix's power, Diesel cackling evilly as this is happening]
Thomas: [turns to his friends] I need you!
Diesel: [cackles] Your little friends cannot help you. I'll pick them off one at a time!
Twilight: We won't be coming to you one at a time!
Percy: We stand together!
Rainbow Dash: Loyalty!
[The beams from the Elements of Harmony combine with the Matrix of Leadership. Thomas smiles bravely as the power of Friendship flows through him]
Thomas: So you see, Unicron, the ones who possess the... uh... Spark of Primus combine both the Elements of Harmony and Matrix of Leadership. Creating the Matrix of... FRIENDSHIP!!!!!!! [sends a rainbow beam shooting out of his spark]
Diesel: Very well then. Bring it on! [fires a ray of Dark Energon]
[the 2 beams hit]
[Then there was a massive explosion]
Brian: [wearing sun glasses] Whoa!
[The smoke covering the scene clears and we view Thomas and Diesel laying on the ground. Thomas picks himself up and walks over to Diesel]
Diesel: [groans] What? What happened?
Pinkie: Diesel's back to normal!
Thomas: You were controlled by Unicron, Diesel.
Diesel: I was?
Rainbow Dash: You can thank us later!
Diesel: Anyways, what happened to Unicron?
Thomas: I vaporized him.
Applejack: We're just glad yer back to normal.
Percy: I feel so sorry for what happened to you.
Diesel: No. You don't have to be. I'm sorry for what I did. And thanks for freeing me. However, I still remain with the villains.
[They see Knock Out arrive. He transforms back into his robot form]
Knock Out: Thomas! I hope I didn't miss out!
James: You missed out!
Thomas: But we are lucky to have you on our side, Knock Out.
Diesel: He's not one of you. He's evil.
Knock Out: No, you're wrong. Because, ever since the Decepticons were disbanded, I wanted to join the winning team. And without further a-do, that happened. And the blackness that was in my Spark disappeared. So, now, I will make you disappear! [fires]
[Diesel, Trixie, Sunset, and the Dazzlings flee the scene and everyone crowds around Knock Out]
Thomas: [turns to the Zed Stacks and Knock Out] You won the day, you guys.
Zorran: No. You're the one who saved the day.
Percy: But you de-immobilized us.
Zak: We know. But Thomas is the one who actually did it.
Zip: Yeah. Besides, he's a Trainbot now.
Thomas: [groans] Whatever? Anyway, thanks, Knock Out.
Knock Out: You're welcome.