In "Snakebit" while the other three Ninja jump out of the way from the wrecking ball, Jay instead jumps ON the wrecking ball and backflips in mid-air and lands on the crane and knocks out the Fangpyre controlling it.
Three words: Ninjas vs. Great Devourer.
Zane unlocking his true potential.
Zane: We're coming for you, Pythor!
How about Kai unlocking his potential? Having to choose between saving Lloyd or retrieving the last Fang Blade, flying out of an erupting volcano in a fireball cradling an unconscious Lloyd, and then passing out from the effort afterwards. Plus he was the one most desperate to unlock his potential.
While we're at it, Jay and Cole unlocking their true potential counts. Jay saved him and Nya by stopping a full speed roller coaster and Cole was able to save himself and his father from heavy rubble.
Nya is able to defeat all of the ninjas and create a alter ego called Samurai X by herself which is pretty amazing.
The battle against the Serpentine in "All Or Nothing". Skeletons return.
Garmadon using the combined power of the Golden Weapons to destroy the Great Devourer.