A rabbit threatens to kill another rabbit. He bites a tuft of fur off of said rabbit but is jumped on before he can do anything else. No blood is shown.
Fiver sees a vision of a field of blood symbolising the warren's destruction.
A rabbit is attacked and killed by a hawk off-screen.
A rabbit is found beaten, he is covered in scars. Another rabbit has his ears torn as a punishment.
A rabbit gets shot offscreen. We see his wound getting healed onscreen.
Two rabbits are hit by a train. This all happens very quickly and there is no blood as they both disappear seconds after getting hit.
There's a lot of blood especially for a PG movie (keep in mind this was released six years before the creation of PG-13, which was developed in 1984).
A total of 63 rabbits are killed on screen in the movie.
A rabbit gets parts of his ears ripped off.
Extremely disturbing violence.
The overall violence is moderate level. It solely involves animals (predominantly rabbits), but it can still get pretty disturbing.