I actually had murder happen in my fanfics XIV, XV, and definitely in XVII.
In XIV, it was carnivorous, but of a far more sinister nature. Basically, a Pteranodon marries a Sharp Beak and things go great for a good while, but, when they have a kid, Sharptooht mom, who gradually grows or is exposed to be, more narcissistic, is envious that her son spends more time with her mate than her. Also, she perhaps wants to make him a Sharptooth whereas her mate had the position to let the boy (Ptero) would choose on his own and that they weren't to influence him unduly any way and he'd choose when he's older.
Eventually, her mate gets tired of her self-centeredness and decides that he's going to take the boy and leave as soon as the boy learns to fly (which is really soon).
His mate lures him to a location and asks him what he's gonna do, which, I guess, is where he reveals his plans. She says that he will indeed be going away for good but that the boy is hers. She then murders and eats him.
However, her mate yelled out to her son before he died. The boy came, though the body was gone. She says that Leaf Eaters killed her mate and stole the body. (The boy wasn't quite aware that his father was a leaf eater and assumed he was a Sharp Beak too). Ptero, her son, believes the lie.
Later, Ptero, now raised to be a hunter, actually would hunt on screen (though the death blow once he caught his mammal prey wouldn't be shown) and later Ptero, hating Leaf Eaters, would encounter Ducky and calously decided he's going to kill and eat her (he hates it when Sharpteeth kill hatchlings but, owing to what he believes happened to his father, believes Leaf Eaters to be very wicked creatures and hence not deserving of any pity). Luckily he fails.
However, Ptero eventually goes good and his mother comes, and, as the boy finds out the truth, threatens to eat the Gang of Five, now his friends, unless he comes along.
Later, she later almost eats Pterano and Mama Flyer out of spite. And, when her boy gets in the way, says she should have known that he'd be like his father and was gonna murder her own son, but was knocked out by Petrie and Mama Flyer and fell to her death in a tar pit.
In XV, some threehorns had killed Topps wife and kids (minus Cera and an older daughter) in a food dispute (this was a flashback).
In XVII: Gallim is a sort of serial killer, both murdering through others, both for food and power. He even gets Chomper to, unwillingly, kill someone, then uses Chomper's killing of the Old One to frame Chomper for all of his crimes.
When he is finally exposed, he kills loads of creatures in the Great Valley before finally being killed by Littlefoot himself.
Gallim's direct and indirect victims would include:
Littlefoot's mother (indirect, though he tried to do it directly)
Littlefoot (always fails)
The Leader of Tippy's herd (directly, for the most part, though a Fast Biter helped)
The Old One (through a very unwilling Chomper, who was forced to do it as Gallim had gotten the Old One to fight Chomper's girlfriend and his girlfriend was about to be killed)
The whole Gang of Seven plus their dates (failed)
Ruby (attempted murder that luckily failed as she was saved by Pterano and Ichy)
The whole Gang of Six plus their dates (failed, and he was ordering the grownups to execute them for treason, i..e friendship with "evil Chomper" too!)
Loads of Swimmers, an Igunadon, two Fast Biters, an Egg Stealer, and a Fast Runner.
Ali (almost worked, but Littlefoot came to her rescue)
Littlefoot (might have worked, but Littlefoot's mother's spirit tells Littlefoot to use the Longneck tail whip, and he does and Gallim loses his own life when Litltefoot tail whips him into lava)
Also, in LBT XVII, it appears that Red Claw murders Chomper's girlfriends parents over power but luckily, it is revealed that they survived in the part 2.
(Note, film XVII is a LBT finale two parter so I can get away with more I think there)
Those would be how far I'd take it.
