The Toa Mata fight Teridax in the Mata Nui Online Game.
Not to mention the speech Vakama gives Takua after that climax of said game. The music that starts swelling as he begins to talk is especially impactful to the tone of the epilogue.
The Toa vs their evil Shadow Duplicates. There are two conflicting canons as to how this fight went down. One had the Toa accept that darkness is a part of them and simply absorb their duplicates. The other featured a truly epic round of opponent switching.
In that second version, special credit must be given to Kopaka, who was the only one of the Toa to defeat his shadow solo... only for the defeated duplicate to multiply into an army of Kopakas. Still better than the other Toa were doing.
2002: The Bohrok Swarms
The Exo-Toa. Giant autonomous suits of armor. That is all.
Prior to that, Onua talking Lewa into ripping the mind-controlling krana off of himself.
Lewa then uses the psychic remnants of the mind control to help defeat the threat.
Kopaka freezing a lava flow and Lewa figuring out how to get past an unsmashable wall: There is nothing that Onua and Pohatu can't break. Therefore, since they can't break the wall, it must not exist. As soon as its nature as an illusion is revealed, the wall vanishes.
During the battle with Cahdok and Gahdok, Gahdok figures out that Gali's weakness is intense heat and proceeds to start giving her heatstroke via continuous blasts of fire. Tahu takes one look at this and simply steps in between them, absorbing the fire with no problem whatsoever and allowing Gali to recover while he singlehandedly holds Gahdok off.
2003: The Bohrok-Kal Strike / The Mask of Light
Tahu leading an entire army of Bohrok to do battle with the Tahnok-Kal. Sure, it ends up backfiring on him, but it was awesome nonetheless.
Kopaka, Gahli and Lewa attempt to use their Kaita form (as demonstrated above) against the Bohrok-Kal. The Bohrok-Kal respond by forming their own Combining Mech and effortlessly defeating them.
The Bohrok-Kal get one for so effortlessly using the Toa Nuva's overconfidence to steal their elemental powers and hand them the worst beatdown they received in the entire series.
When the Bohrok-Kal are about to win, Tahu breaks out his secret weapon: The Kanohi Vahi, a mask that lets him STOP TIME. There's the Godzilla Threshold and then there's that...
From the first movie: The Rahkshi have so far spent their time sinking the village of Ta-Koro (which is a floating rock fortress in the middle of a volcano!). When Takua and Jaller meet up with Kopaka, Toa of Ice, the Rahkshi appear and flings Kopaka down a mountain/glacier by use of a friggin' disintegration beam. Takua, who the Rahkshi were following, grabs the Mask of Light they're after and tries to cross a small lake by using Kopaka's shield as a raft. The Rahkshi can fly, so that doesn't work out too well. But what does Kopaka do the moment he wakes up? He utterly wrecks their shit. An initial blast of his ice power sends all three Rahkshi tumbling into the water, and then a quick stab with his sword freezes the entire lake solid. "Washed and chilled" indeed.
Let me clarify: Kopaka took down three beings who repeatedly wiped the floor with his team in one shot.
Made even better with extended comic canon. After Ta-Koro, three Rahkshi took down Tahu, Gali and Lewa and trapped Onua and Pohatu in a cave full of krana. Kopaka then finds himself facing all six, taking down two solo before backup arrives.
There's also Jaller's Heroic Sacrifice in The Movie when Takua is under attack by Rahkshi Turahk. He does so by literally clinging onto his staff and absorbing all the fear energy from his attack. Nothing says brave like hanging on as pure fear is being pumped into you.
Even more Awesome is when the Takanuva-Makuta hybrid being resurrects Jaller from just his mask. The mask previously worn by Turaga Lhikan, who also made a Heroic Sacrifice to save the hero(s), and was killed by Makuta. Yet Takanuva manages to use some of Makuta's own power to bring Jaller back.
Need I say: The Birth of Takanuva from the BIONICLE film, The Mask of Light. To elaborate, Takua just lost his friend to Rahkshi Turahk and remembers him saying, "You know who you are". He then realizes who he is, shifts his expression from one of grief to one of boldness and determination, dons the Mask of Light, and becomes the very Toa of Light he was searching for. After christening himself as Takanuva, he then one-shots Turahk and finishes revealing the hidden statue of himself as the herald before going off to mourn Jaller.
What, no mention of the epic Takanuva vs Makuta battle? Teridax mockingly challenges him to a game of deadly kolhii, which Takanuva wins. Then, when Teridax gets back up, Takanuva jumps on him and wrenches the Mask of Shadows off the Makuta's face, sending them toppling back into a pool of energized protodermis, fusing them together. Oh, and Takanuva ends up in control of that fusion. He's fused with the mind of the big bad himself, who had intricate plans within plans comprised over thousands of years, and Takanuva out-willpowered him.
The awesomeness is a little undermined by the later revelation that Teridax intentionally lost that fight to keep the Toa off his back for a while.
But built back up again when you realize that everything that the forces of good did in last 1000 years, including all of his "defeats" were part of his master plan.
In the second movie: the protodermis cage. The Toa seal Makuta in a barrier only they can unlock. I repeat. The most powerful villain in the series can't escape from it. Not bad for a couple of rookies with two weeks of experience.
Kind of Fridge-y, but Vakama's creation of the Vahi, the Legendary Mask of Time. Sure, it happens fairly quickly in the movies, but think about it: the Vahi is a mask so powerful, if damaged, Time itself would be undone within the Matoran Universe. There are only two other masks as powerful: the Ignika, the Mask of Life, and Artakha's Mask of Creation. Guess who made those? The Great Beings, more or less the greatest inventors and creators in Bionicle. That's right, Vakama is a mask-maker on par with the creators of his universe. Of course, he did have help from Artakha, who made the mask's composite materials (the Great Disks), but the point still stands.
Similar to the example with Kopaka above, Nokama at one point finds herself trapped in the Metru Nui Archives with three very angry Rahkshi coming after her. Her teammates have all been kidnapped by the Krahka, she is a novice Toa with almost no fighting experience under her belt, she was nearly killed by her best friend less than an hour earlier, and is already worn out from the trek through the Archives, but she calmly assesses her situation and proceeds to engage them in battle. Somebody wasn't walking away from that fight, and that somebody was three Rahkshi.
Turaga Duma AKA Makuta Teridax took control of Metru Nui without firing a shot, easily outgambited the Toa, commanded an army of robot policemen and succeeded in his plan by tricking an entire population into entering stasis chambers.
2005: Web of Shadows
Matau, definitely gets his in the third movie, "Web of Shadows." While the other Toa are fighting the hoard, he manages to escape, find Vakama, and they have a duel, Anakin/Obi-Wan style. In the end, Vakama knocks Matau to the edge of the tower they're fighting on. Matau manages to grab onto the edge to avoid plummeting to his doom. Vakama steps on his hand, trying to get him to let go and fall. Vakama tells him "You are weak, brother." Matau, the ego-maniac who never admits to ever being wrong, then gives this speech as he hangs thousands of feet above the ground: "You're right, Vakama. I am weak... We all make mistakes, Vakama. That's what happens when you're brave enough to make decisions. I understand that now... Wait! I'm sorry. For doubting you. Our strength comes from our unity, Vakama. Which means... you can't be strong without us." Vakama interjects: "I'm better, stronger alone!" Matau continues: "I don't believe that! And I don't think you do, either. You're our LEADER, Vakama. You're my leader. We've got a job to do! ... And if there is any of the Vakama I know left, he'll know what to do." Matau then let's go of the ledge, falling head first to his doom.
This trooper used to absolutely despise Matau, but that scene redeemed him in her eyes.
Vakama, of course, jumps after him with an extremely long vine. Matau laughs gleefully. Moments later Vakama grabs him: "Hang on; I've got a plan."
Also, Keetongu's Determinator act of absolutely refusing to die as he climbs up the tower, is finally shot down, and then rises up and proceeds to kill Sidorak.
This was after the movie, but there are two at the end of Time Trap, one for Mata Nui and one for Vakama. At the end it's revealed that the information the Toa found that revealed that they weren't originally supposed to be Toa at all was manufactured by the Great Spirit HIMSELF in order to convince Teridax to create the Toa he actually wanted. He pulled one over on the ultimate master planner! The other is when Vakama talks Teridax down by [i]threatening to destroy time itself![/i] Needless to say, it worked.
2006: Voya Nui: Island of Doom
The battle between Axonn and Brutaka at the end of the Voya Nui saga. After spending the entire arc just barely surviving and guiding the new Toa toward their destiny, Axonn finally realizes he isn't able to turn Brutaka back from the path he's walking and literally shrugs off everything his former friend throws at him. He also has one of the best lines in the series during this fight:
Brutaka: "You fool, Axonn! Don't you realize you're fighting for a lost cause?"
Axonn: "Don't you realize? Those are the only kind worth fighting for."
Please note that Axonn's superpower is the ability to get so angry that nothing can hurt him. When Brutaka realizes that Axonn has gone into that level of rage, he freaks out and tries to teleport Axonn into ANOTHER DIMENSION believing (from experience) that it's the only way to stop him. It doesn't work.
2007: Mahri Nui: Sea of Darkness
Karzahni (ruler of Bionicle hell) vs. Teridax (Big Bad who knocked out God). After a sort-of stalemate, Karzahni uses his mask to torture Teridax by showing what will happen if Mata Nui wakes up. Teridax screams for a bit before promptly ripping Karzahni's psyche in half. Then Brutaka shows up, has a Heel-Face Turn, fights Teridax to a stalemate and steals back the Staff of Artakha.
Matoro sacrificing his life to resurrect Mata Nui. Just... damn.
Said sacrifice also burning out the eye sockets of three Makuta with the glow from the process, as if reviving the Great Spirit wasn't enough.
And just before he goes, Matoro calms himself with theBadass Boast. Very few lines will ever beat the sheer awesome of:
"Turaga Nuju always said the universe was a riddle. Today, I am the answer."
The Toa Hagah, in one of their first actions after being transformed back from the Rahaga, stop a massive kaiju battle between Tahtorak and the Kanohi Dragon. In reference, it took a team of eleven Toa, including Lhikan, Nidhiki, Tuyet, and four Toa of Ice, to take down the Kanohi Dragon alone the last time it rampaged. Kualus disabled it singlehandedly.
Takanuva gets repeated ones against the Makuta in Karda Nui. On more than one occasion, the darkness he got infected with influences him to get seriously pissed off against them, and he may well have killed them all singlehandedly had the other Toa not been present to calm him down.
"But I'm not my "kind", not anymore — your shadow leeches saw to that. I'm half Toa of Light, half Toa of Shadow. This was what you wanted, wasn't it? Toa consumed by darkness, Toa not hampered by things like mercy or morality. Well, now you can choke on it."
Onua has a rather big number of these, oftentimes Big Damn Heroes-worthy. Of particular note is curbstomping Gorast when the Makuta is on the verge of murdering Gali, then doing it again when Gorast tries to lure him over to the dark side.
Another moment for the Toa of Earth is when the Nuva learn they must awaken the Bahrag, and in turn the Bohrok, as part of the preparations for awakening Mata Nui. While the rest of the team is unsure about the task, it's Onua who steps up to the plate and releases the Bahrag, saying that he did what was necessary — after all, nobody ever said the path to the future would be an easy one.
The Heroic Sacrifice ending the Mahri Nui arc was such an awesome sacrifice that the Kanohi Ignika itself was impressed, and then made itself a Toa body to try to become a hero — and then sacrificed itself when asked what Matoro would've done in its situation.
The Reveal of Makuta Teridax'sEvil Plan come to fruition. Who else would have planned to allow the Toa Mahri to bring Mata Nui back to life so that he could enter his body before Mata Nui could, so that when the Toa Nuva finally succeed in reawakening him, he could announce that he won, and seal the deal by sealing Mata Nui's spirit in the Kanohi Ignika and ejecting it into space, taking care of the two biggest threats to his rule?
It's even better than that. Teridax sent all of his most elite Makuta minions into Karda Nui, not to stop the Toa Nuva, but to be in the area when they succeeded, wiping them all out and leaving Teridax as the ONLY Makuta left in the universe.
2009: Bara Magna: Glatorian Legends
Mata Nui vs Tuma. That is all.
2010 and beyond: Journey's End / Sphereus Magna
Mata Nui pushing Teridax into the path of Aqua Magna, causing him to get MOONED! (head crushed by the planet, pulled in by the latter's own gravity powers.)