Status effects affect mobs in unique ways.

Status effects in Minecraft have shockingly little use against mobs, except for basic ones like Strength, Speed, Poison, etc. I think that more mobs should have unique reactions to status effects (fish can breathe on land with water breathing, snow golems with fire resistance don't melt, etc.) to make the world feel more alive and fleshed out and potentially add more use to potions.

I am fully aware that a lot of these status effects cannot be applied to mobs in Survival. Nevermind the fact this would still have a use for mapmakers and Creative players, it serves as a foundation if these effects were to become more accessible in Survival in the future. So if Blindness or Mining Fatigue potions WERE added at some point (for example), they would instantly be useful in Survival.

If you see any of these you think should be removed or changed, or if you have your own ideas that you think should be added, feel free to leave them in the comments.

STRENGTH/WEAKNESS

  • Goats with Strength inflict more knockback when ramming (vice-versa with weakness).
  • Iron Golems with Strength toss targets into the air farther (vice-versa with weakness).

HASTE/MINING FATIGUE

  • Haste increases the speed at which mobs can attack (vice-versa with mining fatigue).
  • Zombies can break down doors faster if they have Haste (vice-versa with mining fatigue).

BLINDNESS

  • Mobs with Blindness have their detection radius reduced, so they will notice targets from farther away. This stacks with Invisibility. Mobs that fire projectiles (skeletons, blazes, etc.) have their accuracy reduced, increasing the spread of their projectiles.
  • Endermen with Blindness don't get mad if you look at their eyes (except at close range).

GLOWING

  • Any mob or player with Glowing effectively causes all mobs to have a higher detection range against them. So if you have the Glowing effect, Zombies (for example) will begin to chase after you from farther away. This can also help your pets/golems detect hostiles from further away.

NAUSEA

  • Mobs with Nausea walk erratically and in random directions, having their pathfinding messed up. Mobs that fire projectiles may occasionally miss and hit one of their buddies, triggering infighting! They also have slightly less accuracy with projectiles in general.

REGENERATION

  • Since Instant Health acts like Instant Damage when used against the undead, Regeneration should do damage over time to the undead like Poison.
  • Regeneration decreases the time it takes for baby mobs to grow into adults.
  • Regeneration increases the rate at which Chickens lay eggs.
  • Basically, you can use Regeneration potions as a sort of "animal bonemeal" to speed up animal farming in the same way you'd speed up crop farming.

SPEED/SLOWNESS

  • Endermen with Speed have shorter cooldown between teleporting (vice-versa with slowness).
  • Flying mobs fly faster if they have Speed (vice-versa with slowness).

FIRE RESISTANCE

  • Creepers with Fire Resistance cannot be ignited manually using a Flint And Steel.
  • Any mob immune to fire (blazes, striders, magma cubes, etc.) will slowly regenerate health when touching fire or lava if they have the Fire Resistance effect.
  • Spiders do not turn neutral during the day if they have Fire Resistance.
  • Bees are unaffected by campfire smoke if they have Fire Resistance.