Wyzen, the very first major boss in the game, is a herald of the awesome to follow. The fight starts rather simply; Asura fights human sized Wyzen and then grinds his face in the ground and throws him off a cliff. Wyzen turns into his Vajra form and is now tall enough to tower over Asura even when standing on the bottom of the cliff over which he just fell. He then grabs Asura and throws him clear over a horizon, and then the real fun begins.
Asura charges at Wyzen, dodging his attacks by using the loose earth brought up by Wyzen's ground punch. He dives down Wyzen's massive arm to give him a good ol' punch to the face, before Wyzen slams him into the ground, jumps into the air, and then slams his ass onto Asura with his 100 ton teabag! As Wyzen keeps attacking, Asura remembers his daughter's cries at being taken from him, and then catches Wyzen's fist and grows his four extra arms, the first time he's ever done so without Mithra's help. Wyzen orders his Septentrion ship to attack Asura, but Asura destroys the ship with just one Ki Attack. The two face off; at one point, Asura catches one of Wyzen's missiles in mid run and throws it back at him! They eventually jump into the air, with Asura catching Wyzen's finger and throwing him by it. Wyzen counters with his famous KurikaraFudo Uchi, while Asura eventually punches straight through the attack, hitting through Wyzen so hard he stretches like silly putty and is sent into outer space!
The fight against Augus on the Moon is also completely insane. Augus remembers how they always used to fight like they will do soon. Asura tries to punch Augus in the face, but Augus just laughs and punches Asura into a wall, forcing him to turn into his six armed form as the true fighting begins. As they fight, they eventually collide their punches with each other, then initiate a Pummel Duel similar to God Hand or Fist of the North Star with the occasional MadWorld-style Cross Counter. Eventually Augus is knocked back, but he gets back up and starts powering up, Battle Aura and Chunky Updraft included, stating that even having sex with the best women Heaven can give him and drinking the best wines of all of Gaea cannot compare to the thrill of using his blade. Back in the Emperors' room in Shinto, while Deus and Yasha watch the battle unfold, Yasha states the only other person Augus has used the blade on is Deus himself, just to state how badass Deus is. They both wonder how Asura could do the same.
The second part of the fight starts with Augus using a Getsuga Tensho like slash, telling Asura to show him what he's made of. His blade is already large enough to carve out a canyon on the surface of the Moon when Asura catches it and throws it aside, but as the battle turns more heated, Augus will extend the blade, until it is so huge that, when Asura catches it, he is pushed off the Moon and back down to Earth, where the blade pierces through him and straight through the Earth! Eventually, as Augus falls towards the ground, Asura punches the blade, breaking it off near the hilt and sending it flying into the air, catches it in midair with his friggen teeth, and slashes Augus in half across the stomach. After Augus dies, a massive Gohma with an Insane Impurity level appears with an entire army of Gohma, heading towards the village and Asura. What does Asura do? Take the broken remnants of Augus's blade and then go to fight the incoming Gohma. It must be seen to be believed.
When the Burst meter in the first battle is full, Asura grabs his extra arms and hits Ryu with an absolutely gigantic Shoryuken that sends both men to the freakin' Moon.
If Evil Ryu hits the Messatsu-Goshoryu Ultra on Asura, he manages to return that huge chunk of land that Asura and Augus unearthed back into the ground.
Asura's grounded attacks on Evil Ryu during the fight include a fury of punches that culminates with Asura performing a SIX-ARMED SHORYUKEN and a modified Muscle Buster which Asura performs with his six arms. Let's say that even after being possessed by the Satsui No Hado, Ryu isn't immune to a good old Groin Attack.
By the time the fight comes to a close, Asura attempts to perform the Shun Goku Satsu to finish the battle. Evil Ryu attempts to perform a Shun Goku Satsu of his own. The two attacks cancel each other out with Asura and Evil Ryu in Back-to-Back BadassesAss Kicking Pose just as a regular Shun Goku Satsu is performed and ended.
Asura vs. Akuma is even better. The Oni fight and the very ending are easily some of the coolest moments in the game.
While not part of the actual battle, Akuma blasting Ryu back to the Street Fighter universe with the Demon Armageddon is pretty cool to watch (and looks less awkward than it does in Street Fighter IV.)
During the Mantra Asura vs. Oni battle, the latter will attempt to perform his Super Combo as well as both of his Ultras. With the mighty power of Quick Time Events, you can freaking counter them.
And to top it all off, the ending of that episode implies their fight continued for 500 years.
The fight with Deus in Chapters 16 and 17 are crowners for all parties involved. On one hand Asura finally gets to lay the smack-down on the one responsible for his suffering, and on the other Deus finally gets to show why he is the leader of the Seven Deities, going toe-to-toe with both Asura and Yasha simultaneously and easily holding his own until the end.
But the Final Boss takes the cake. Fighting it is the whole last level. All of the Callbacks, all the explosions, and the battle IN THE EARTH'S CORE!
As Asura flies through space, he fights Chakravartin by destroying the basic projectiles thrown at him, punching straight through planets, meteors, and even small stars! When Chakravartin causes a sun to go nova on Asura to kill him, Asura blows it up. This, just the first phase of the fight, ends when Asura literally punches through Chakravartin's forehead, which is so big even the planet-sized Asura looks like a flea by comparison.
In the second phase, Asura makes it to the event horizon of Naraka, and as a reward, Chakravartin lets Asura take Mithra back... if he replaces him as the Creator. Asura thinks for a few minutes, then smiles and punches him in the face! A furious Chakravartin shows off his power by breaking the event horizon with just a stab of a spear, and then he and Asura fight again, except Asura is regular human size now. The above forehead punch happens again, but this time, Asura breaks through the event horizon as well! Eventually, Chakravartin ditches the spears and goes full on Pummel Duel against Asura. But Asura triumphs despite having his extra arms broken, ShoryukensChakravartin in the face, and then does a massive Hokuto Hyakuretsu Ken styled attack.
But it's still not over! Chakravartin assumes his ultimate form and stops Asura in his tracks with one finger, reverting Asura back to a more powerful version of his base form. Chakravartin uses a wide area attack, his mere presence now turning the previously colorful event horizon completely white, along with a massive array of similarly visually staggering and powerful attacks. The enraged Asura gives a massive punch to Chakravartin's torso, the energy of which keeps building up, then knocks him back with a more powerful version of the laser finisher used on Deus. The uncomprehending but irate Chakravartinunleashes his QTEs. As the fight grinds on, Asura gives an awesome "World of Cardboard" Speech and calls out Chakravartin for only wanting to rule the world, then knocks him off his feet, forcing Mithra out of his grasp. Though Mithra protests that he will die if he kills Chakravartin by overusing the Wrath mantra and that all the living civilian Demi-gods will become mortal, Asura just smiles to Mithra and delivers a massive punch that destroys Chakravartin and Naraka with it!