The Riftwar Saga (Magician, Silverthorn and Darkness at Sethanon)
Arutha's winning the day during the Riftwar against the Tsurani. Not only does he throw himself into combat without hesitation, he outright stops the Tsurani attacks temporarily and wins the Undying Loyalty of the soldiers he fights alongside with.
Amos Trask getting through the Straits of Darkness when it was almost winter, something very few sailors, if any of all have accomplished.
Martin disabling a tiller in Magician on a ship that was chasing them from a distance when escaping from Krondor.
Pug's unleashing magic at the arena in Kentosani, which even Macros the Black was impressed by.
Macros' unleashing the magic of Elvander and it's creatures on the Tsurani invading Elvander.
Martin's standing up to Tomas when Ashen-Shugar's influence has a full hold of him and he's executing Tsurani prisoners in cold blood, despite having absolutely no chance of winning.
Arutha, Martin, Laurie and Jimmy go out on a fool's errand to attempt to get an antidote to save Anita's life when she's accidently poisoned and succeed despite all odds.
Pug's unlocking his ability to use the Lesser Path and escape when he's held hostage and is being tortured for information in an Anti Magic chamber.
Guy du Bas-Tyra's strategy of igniting the naphtha mines beneath Armengar and blowing it sky high after luring in a significant part of the moredhel armies.
Pug and Tomas go off on a mission to find Macros and travel to many worlds and even go outside of Time itself and succeed. During this adventure, they fight off a black dragon and a Dread and then with Macros' help, stop the End of the World as We Know It in the climax of the book.
Speaking of said climax, the duels between Arutha and Murmandamus, and Tomas and Draken-Korin both have to qualify, particularly the second one. It's the first time in the series that Tomas has faced an opponent who possesses the power to kill him, and the battle is accordingly ugly.
The Riftwar Legacy (The Krondor: books and Jimmy and the Crawler)
Another one for Jimmy/James. Setting up a intelligence agency for the entire Kingdom and having spies everywhere except for Queg. This lasts until the Chaosaga, the final arc of the series. At least a century after he died.
William being aided by Kahooli, God of Vengeance to defeat Bear who has proven himself to be Nigh Invulnerable due to the Nameless One's amulet around his neck.
Arutha fights a demon summoned by a cult and slays it without taking any hits at all.
Krondor's Sons (Prince of the Blood and King's Buccaneer)
Borric is captured by slavers and escapes, but instead of just going home, he goes all the way to the city of Kesh where he was meant to go and helps his brother Erland stop a coup against the current Empress.
The Serpentwar Saga (Shadow of a Dark Queen, Rise of a Merchant Prince, Rage of a Demon King and Shards of a Broken Crown)
The husband/wife team of Duke James of Krondor (aka Jimmy The Hand) and the telepath Gamina blowing up the whole city of Krondor using medieval technology to destroy an enemy army. This is arguably the greatest Heroic Sacrifice in all of High Fantasy. And the best part? They didn't feel a thing as their bodies died, as Gamina used her powers to overwhelm both their senses with memories of every joyful moment they had together over 40 years of marriage.
Nakor's tricking the Panathians into burning the ship manufacturing factories down. Also doubles as a Crowning Momentof Funny.
Anytime Pug puts Patrick in his place in the Serpent War Saga.
The Conclave of Shadows (Talon of the Silver Hawk, King of Foxes and Exile's Return)
The Dark War Saga (Flight of the Nighthawks, Into A Dark Realm and Wrath of a Mad God)
Pug dropping the Kelewan moon onto Kelewan to stop a Dreadlord from emerging into the First Plane. Even Banath was impressed by that.
Not to mention how Nakor lured Leso Varen to him and permanently killed him, something that Pug couldn't accomplish in the century or so since their first encounter.
The Demon War Saga (Rides a Dread Legion and At The Gates of Darkness)
The Chaos War Saga (A Kingdom Besieged, A Crown Imperiled and Magician's End)
The ending for Magician's End. Yes, Pug and Tomas are dead, but the Dread have been stopped and peace has returned to Midkemia for who knows how long and Magnus still lives on, so Midkemia will always be safe.
Other (Empire Trilogy, Legends of the Riftwar, etc)