I think this one is kind of self-explanatory given the novelization of the film actually chose to portray Sharptooh's morality as being more pinned to a given interpretation than how vague it was in the actual film, albeit this interpretation here could very easily apply to the film as well because of how little it actually changes the overall events of the plot as we already know it unfolds.
Sharptooth, in the novel, is described as being a Serial Killer who preyed on the Flatteeth not just because of hunger, but actively killed Flatteeth out of a mad blood lust he has which makes him a serial killer compared to other Sharpteeth who simply tried to survive. Sharptooth was hunting for new victims, and when encountering Littlefoot and Cera, had every intention of killing those two because Littlefoot had wound up wounding his pride by having a sharp thorn pierce his eye and leave him half blind afterwards, and his pride further being wounded by Cera when she headbutts him while he's unconscious. Then of course the fact Sharptooth killed Littlefoot's Mother while being fully aware of the fact he was doing so less out of a need for food and more so to kill for the sake of it. He had apparently discovered the entrance to the Great Valley as well, and had every intention of heading there to go on a killing spree, but his own pride got the better of him, leaving him with a score to settle with five children who offered no real sustenance for him, and he targeted them specifically because of Littlefoot and Cera's presence in the group, reminded of the fact that the two of them damaged his pride and left him irrationally hateful towards both of them by the end. Even when nearing death, he attempts to take Petrie with him at the last second solely out of a spiteful attempt to have the last laugh in the end.
Definitely makes you think about Sharptooth in a different light when you consider he's flat out the most menacing incarnation of a carnivorous dinosaur in virtually all of The Land Before Time's franchise wide history of many other Sharpteeth after him typically not showcasing the same behavior he had which made him stick out more.
