The Killer Bunny isn't available in the Bedrock version of Minecraft, but only in older versions of Java, and it has to be spawned by the player in the world. If it is spawned during creative mode ...

Bad Omen from Ominous Bottles in Minecraft can enhance challenges & rewards for players, potentially spawning new mobs and events. Spawning the Killer Rabbit & Zombie Horse with Ominous effects ...