Here is how Crooler tamed Rudy in The Overlord Returns.
With not much to lose, Crooler had to save Luna.
Crooler: I know what I must do the save Princess Luna.
Cragger: Be careful, Crooler, Rudy is dangerous!
Crooler: I have to try my best, brother.
So, Crooler came closer to Rudy.
Star Swirl the Bearded: What is she doing:?
King Crominus: I think we're about to find out, Star Swirl.
Crooler: Here, Rudy. I'm not going to harm you.
Crooler started petting Rudy, he didn't see her as a threat to him.
Crooler: I just want you to spit out the princess.
Stygian: I hope Crooler knows what she's doing.
Sensei Wu: We must keep our hopes up for her.
Princess Celestia: If it means saving my sister, Crooler must save her.
Shifu: We must ensure of this.
Rudy was touched by Crooler, petting him gently.
Crooler: It's true. I know it. You don't mean to destroy everything. When, uh... when people look at you, they see a monster. But I know that you just feel scared and alone. I know how that feels.
With that said, Crooler's eye filled with tears.
Crooler: To be judged unfairly. So, um... I just wanna say that you're only hungrier for a reason.
With one deep breath, she started to apologize to him.
Crooler: And... I'm sorry. (sighs) When you had to crave on the alicorns.
Then, Princess Luna could hear Crooler speaking to him.
Crooler: And that you could've find any meat of your own. I wish we could help you, and... treat you nicely.
With that said, Rudy spat out Princess Luna who was relieved to be free.
Princess Luna: Thank you, Crooler. I owe you my debt.
Crooler: Think nothing of it, Princess Luna.
Princess Luna: Though, I am a little curious. Did you mean all those things to Rudy?
Crooler: Yeah.
Princess Luna: Well, I have a hunch in my heart that Rudy feels the same way.
Crooler: Obviously.
Suddenly, the Overlord then appears in a giant mech with a massive cannon as its left arm.
The Overlord: It's over, heroes. And unfortunately for all of you, my mech is immune to every attack you make, making it invincible.
Po: In case you forget, Overlord. You were beaten twice by the Ninjas as well as Lord Vortech was beaten by the Master Builders once.
The Overlord: Don't you think I thought of that?!
Lord Vortech: It's time we put an end to this.
With quick thinking, Po started dodging every attack they threw at him.
Po: Is that the best you got?
The Overlord: How're you dodging?!
As the Overlord fires his attacks, Po dodged again and again.
The Overlord: You're forgetting one thing. My mech is immune to everything you got.
Po: But you don't have enough take the Dragon Warriors down easily!
Lord Vortech: (as Po kept dodging) Stop moving!
Cragger: Po, what're you doing?!
Po: Fighting them without even hitting them!
As they realized the Silent Fist, Po kept using the technique to tire them down.
The Overlord: Enough!
Po: What's the matter, Overlord, running low on your fire power?
With Po using his Silent Fist, the Overlord was getting tire out.
The Overlord: That was it? That was all you've got?!
Soon, everyone else had to join Po to fulfill the prophecy.
Eris: Stop this, Overlord. Why are you doing this?!
The Overlord: Because your time is over!
Emmet Brickowski: Not as long as we use our secret weapons to defeat you all!
Star Swirl the Bearded: Twilight, Stygian, open the portal!
As Stygian was about to open the portal, Zane make ready to use his ice power
The Overlord: Oh no you don't! (tries to fires at Stygian but was frozen) What, what's happening!?
Stygian: What's happening to the Overlord?
Zane: My ice power has the ability weakening the Overlord.
The Overlord: That's impossible! My mech is suppose to be immune to everything! (shatters the ice)
Po: Let's finish them off for good!
Zane: I'm ready when you are, Po!
So, they use every amount of Chi allowing Zane's ice power to freeze the Overlord, the Preeminent, Lord Vortech and the rest of the LEGO Villains including Overlord Vortech.
Sir Fangar: They have felt the freeze!
Star Swirl the Bearded: Now, Po! Push them all in!
Po: Let's all do it!
So, Po, Twilight, SpongeBob, Laval, Lloyd, Emmet, Batman, Wyldstyle, Gandalf and all of their friends used their Chi technique allowing their energy to push them into the Portal to Tartarus.
Po: Skadoosh.
Just as the Overlord broke the ice, the portal finally closed on them.