Just as it looks like Littlefoot and Cera are about to be devoured by the Sharptooth's toothy maw, cue Mama Longneck's massive tail, which smashes the predator off its feet and into a mound of rock — she then proceeds to take on the Sharptooth single-handedly.
And not only that. The fact that a group of little dinosaurs manage to outsmart and KILL Sharptooth, the most deadly predator in all of the films, is pretty awesome.
AND not only THAT, the plan in question that Littlefoot conjures up to get rid of Sharptooth after getting sick and tired of running away from him is so gloriously thought out and said to the gang, that it makes him look badass and is just plain awesome.
And also, Cera coming back to help Littlefoot, Spike, and Ducky push the boulder the Sharptooth is on into the water, screaming, "I'M COMING!"
The Lone Dinosaur from #6: a celebration of badass longnecks. His John Wayne-esque voice doesn't hurt things either.
Also from 6, The 2v2 battle at the very end.
In a scene that's a Crowning Moment of Awesome, Crowning Moment of Heartwarming, and a Crowning Idiot Hero Moment all at the same time, from 5 where Littlefoot ends up jumping off of a cliff into a shark infested ocean to save Chomper from drowning.
Not to mention the fight between Chomper's parents and the enemy sharptooth.
In number 10, the final fight between the longnecks and the sharptooths. Doubley so because we finally see Grandma and Grandpa Longneck in a fight!
Actually they've been in fights in previous movies, and they do a good job at them for dinosaurs at their age.
In number 9, Mo taking on the Sharptooth Swimmer all by himself, including taunting it, slapping its face with his fins, and just generally owning it.
From number 7, Petrie Calling the Old Man Out against Pterano's visions of a new world, when what they had in the great valley was perfectly wonderful.
In number 3, Cera standing up to her father for his stubborn parenting, to the point where he's practically at a loss for words.
In number 12, Guido discovering he can glide and uses this ability to save Tricia from being swept away in a river. And then Petrie and his siblings all pitch in to save the two when Guido gets caught in the water himself.