Here is the scene where Dark G-Merl is now back to G-Merl in War of the Apocalypse.
Tino Tonitini: G-Merl! You don't have to do this!
Dark G-Merl: Oh I would, vengence might make a difference with you out of the picture.
Ash Ketchum: You got to come back to us! Pikachu, Thunderbolt!
(Pikachu unleash the thunderbolt attack, but Dark G-Merl bounches the attack using his X-Blade as a shield and hits Pikachu instead)
Ash Ketchum: Pikachu!
Dark G-Merl: (Laughing Evilly) You see, what I told you. You cannot defeat be!
Tai Kamiya: Yes, we can!
Dark G-Merl: Shut up, leader of the DigiDestined!
(He fires Dark Firaga and hits Tai)
Agumon: Tai!
Kari Kamiya: Get up, Tai!
(Dark G-Merl grabs Tino from behind and chokes him)
Dark G-Merl: No more delays! I'm gonna kill you now, Tonitini. Then everyone else.
(Tino looks at Sunset Shimmer as she nods at him)
Tino Tonitini: This isn't the way! I know you feel powerful right now, like you can have everything you want! I've been where you are, I've made the same mistake you're making! I've gotten my rainbow powers and just like you, I was overwhelmed by the magic it contained! I thought that being with Sunset would get me everything I wanted...
Dark G-Merl: Oh, you're wrong. Unlike you, I shall have everything I desire!
Tino Tonitini: No, you can't, there is a difference between you and me. (he jumps behind Dark G-merl and kicks him and then, Leatherhead grabs hold of him) We both looked into the abyss. (Sunset Shimmer stands beside him) But when it looked back at us. You blinked.
Sora: He's right, It's time for you to face the light!
(Sora holds up his Keyblade and creates a sphere, which engulfs everything in light as Tino and Sunset Shimmer use their power and blast it at Dark G-Merl and causes it to return to normal)
Dark G-Merl: Noooo!
(G-Merl is floating in a white void afterwards)
G-Merl: I'm...fading... Fading away...into the light.
(G-Merl looks and sees Tino as he came closer)
Tino Tonitini: Take my hand, G-Merl. Let me show you there's another way... just like someone once did for me.
(G-Merl lets his hand grab Tino's hand as the entire light and the white background fade away)
Emerl: Tino, G-Merl!