[SPOILERS]
Fecto Forgo absorbs a dog into its body along with several other animals. When it is finally well and truly killed, you can see animals it absorbed flailing around before dying.
Subtly, but in ways that are pretty creepy. The true final boss has pitch black eyes with tiny red pupils that follow the direction of the camera. What makes it eerie is that the model is shown always making eye contact with the player, NOT the character of Kirby himself.
[[SPOILERS]] While not a baby, the main antagonist of the game takes the form of what appears to be a fetus when you first meet it. It also appears in this form during the battle to get the true ending.
Leon dies - twice, in fact. Both times, Kirby is the one who kills him, and then his body continues to be used by Fecto Forgo. Both times he is brought back to life.
Fecto Forgo absorbs many animals into itself, which all are grotesquely integrated into its monstrous, amorphous body. When it is finally killed in the postgame, all of the animals it absorbed can be briefly seen flailing about from the ball of light it becomes before dissipating.
There are a few major bosses who are felines. One non-graphically explodes into dust and stars like other enemies. After the ending and the true ending, they both are shown to be alive and well.
There are snake-like enemies that attack Kirby by lunging at him. However, the snakes themselves are very cartoony in style & Kirby can easily escape/avoid them.
A boss is shown to be possessed on-screen multiple times, and multiple enemies are shown to be assimilated into the same body as the possesser. There are multiple off-screen, implied, and referenced possessions.
technically no, but one of the fights before the final boss has an attack where a lazer is shot out of his mouth, and the animation that indicates it looks a lot like he's trying to hold you know what in. it's not very triggering and even i didn't notice until someone pointed it out, but it's still worth noting.
One of the bosses shoots a dark red liquid as one of its attacks, which makes an audible splat noise on impact with the ground. This dark red liquid can be very easily interpreted as blood.
In many situations, the camera snaps to focus on a boss if it moves very fast. One boss also has an attack where it violently shakes the player character back and forth, with the camera violently shaking as well.
A few menu graphics sparkle, spin, or move. When the player character or an enemy gets hurt, they flash white, and stars also momentarily appear on-screen.
Many of the abilities the player character can use involve flashing particle effects.
A few dark areas involve constantly turning a light on and off.
Many levels late in the story involve fire and flames, which flicker.
In the last area of the main story, there are a few graphics stylised to glitch and flash.
In post-story areas, glitters of light float in the air.
There are other fast-moving or rapidly-disappearing particle effects used following attacks, or the star that the player character rides on.
(SPOILERS)
For the last part of the final boss, Kirby inhales a truck and crashes into them. the boss is heavily implied to die but nobody is shown and the actual hit is partially obscured by light.
The final boss of the main game melts into a gooey mass during one fight, and during another, starts and continues to drip goo during the final phase. The latter fight is not graphic, and in both fights, the goo is not blood-coloured.
In fights with the final boss separate from the main mode of gameplay, upon entrance to its second phase, the boss melts into blood-coloured liquid. This blood-coloured liquid remains on-screen as floating spheres. One of the boss' attacks involves shooting this liquid at you like a high-pressure water gun, and an audible wet impact noise can be heard. During its reformation after that attack, the particle effects look very much like floating blood splatters.
Fecto Forgo absorbs a dog into its body along with several other animals. When it is finally well and truly killed, you can see animals it absorbed flailing around before dying.