This is how Tahu de-corrupts the Toa goes in The Return of Harmony Part 2.
[Tahu goes to Onua's cave]
Onua: And so I tried to defeat the Lord of Skull Spiders, but none of my so-called "friends" would lift a hand to help me.
[Tahu comes in]
Tahu: Onua, I'm here to fight for our friendship.
[Click licks Tahu]
Onua: Oh, now you want to fight. Where you went when I was battling the Lord of Skull Spiders?
[Tahu tackles Onua to the ground]
Tahu: Snap out of it. This isn't you! You're not a liar.
[He uses his magic on Onua and his colors return]
Onua: Wh-what happened? Tahu! [sigh] I saw a vision of us feuding and fighting. I couldn't face the truth, so I started telling lies. Can you ever forgive me?
Tahu: I already have. Come on!
[They later de-corrupt Kopaka]
Kopaka: Oh no! Tahu, Onua, I just had the worst dream!
Pohatu: [off-screen] What do you think you're doing? Get away from my gem! Get away--!
[Pohatu is de-corrupted]
Pohatu: [grunting] Let us never speak of this again.
[Lewa is later de-corrupted]
Lewa: [laughter] And I-I turned gray! [giggle] Can you believe it?!
[Later on, they look for Gali]
[They meet up]
Kopaka: Uh? She's not here.
Tahu: Without Gali, we can't use the Elements.
Onua: She could be anywhere by now! We're never gonna find her.
Lewa: Yeah, we will, 'cause she's right there!
[They look down and see Gali in a pool of water]
Gali: Hey, guys!
Tahu: We've been looking everywhere for you!
Gali: That's nice.
Tahu: The Lord of Skull Spiders' still on the loose! We need you to help us defeat him with your element, Loyalty!
Gali: Pfft. Loyalty, schmoyalty! Have you guys seen Ponyville? It's a disaster! I'm staying here in the water where everything's awesome.
[She swims away]
Pohatu: How in Equestria can she think that patch of water is awesome?
Onua: The same way he got you to think that cheap rock was a bona fide diamond.
Pohatu: I thought we agreed never to speak of that again.
Tahu: Time for Plan B.
[They track Gali to the lake]
Tahu: [whispering] Okay, Kopaka, you grab Gali and hold her down. Onua will lower me down from this rope so I can cast the memory of our friendship on her.
Kopaka: Got it!
[He creeps up on her]
[She wakes up, noticing Kopaka]
Kopaka: Um...I'm just wondering if it's okay if I hold you down against your will for a little bit?
Gali: Nice try! Ponyville's your problem, not mine.
[She swims away]
Tahu: Come on, Kopaka, we've got to catch her. Hyah! Onua!
[They chase Gali]
[Lewa and Pohatu are pulled along]
Pohatu and Lewa: WHOA!
Pohatu: LEWA! You were supposed to secure the ROPE!
Onua: Pohatu, Lewa, hold on! You all are slowing her down!
Pohatu: Oh, Kopaka, would you be a good Toa and GO FASTER, please?
Kopaka: [grunting] I can't!
Tahu: If you can't catch her, the Lord of Skull Spiders wins!
[He runs on]
Kopaka: That big... dumb... MEANIE!
[He catches Gali and ties her down]
Tahu: Okay, Onua, last rope! Make it count!
Gali: Lemme go! I don't need you guys! Leave me alone!
[Tahu de-corrupts Gali]
[Her colors return]
Gali: Wh-what happened? [gasp] How's Ponyville? Where are the Elements?! Did we stop the Lord of Skull Spiders?
[They all smile]
[They see the Lord of Skull Spiders' chaos and back off]
Tahu: Maybe it's a little early for a group hug.