Pretty much all of the epic battle sequences, including:
The Battle of Tertae Fields at the end of The Warrior Prophet. Beseiged and starving, the Inrithi have turned on each other and sentence Kellhus to Circumfixion. When he miraculously survives and pulls Serwë's heart from his own chest, the feeble Inrithi are inspired to heroic deeds. They pour out of Caraskand and attack their far stronger foe, empowered by unconquerable belief, and win.
The Siege of Shimeh, featuring a full throw-down between the Scarlet Spires, the Cishaurim, the Imperial Saik. Achamian's duel with a demon and Kellhus's fight with a half dozen of the top Cishaurim alive also factor into the affair.
In The White Luck Warrior, the Great Ordeal stages a last stand against a tide of sranc while Sorweel's company rides to warn the army of the Ten-Yoke Legion's sneak attack. When Sorweel rides back, he sees what he thinks is a hopeless battle, but soon realizes that the Great Ordeal is singing as they slaughter, that he's not witnessing certain defeat, but glory.
In The Judging Eye, when Mimara banishes the Wight-in-the-Mountain and shuts the gates to the afterlife.
The final scene of The Thousandfold Thought, which doubles as a Tear Jerker.
Almost any time Achamian gets to demonstrate why the Gnosis is so respected. For example, attacking a group of Imperial Saik sorcerers and their Grandmaster, killing all of them single-handed, and then fighting off the most powerful demon Iyokus could send after him.
Achamian and Cleric defeating the Father of Dragons in The White-Luck Warrior.
The giant Oirûnas arriving, in full battle regalia, to take on the Vile court of Ishterebinth.
Kellhus arriving to single-handedly defeat Fanayal, Meppa, Psatma Nannaferi and Malowebi, while delivering some deadpan snarks along the way.
Achamian gets ambushed by nine enemy sorcerers and still takes out four of them before being captured. He subsequently tears apart the compound they were holding him in, defeats a demon summoned to hold him off, and then tracks down and ironically blinds his torturer. At another point, he defeats the Grandmaster of a rival School, and then proceeds to lay into an army.
Anasûrimbor Kellhus gets many of these. At one point in battle he starts what looks to be a weird twisting dance. It's only when the observer gets hit that he realises that Kellhus is dodging around a hail of arrows. Later in the same battle Kellhus is charged by a significant part of the Fanim army. "They came galloping toward the circle described by his sword."
Ikurei Xerius, with his conversation-ending one-liner to Maithanet in the second book.
Coithus Saubon killing seven of the Fanim prince's elite guard single-handedly in the first real battle of the Holy War.