Minecraft wiki entry for Defeating_a_woodland_mansion, associated text: A pair of elytra (with firework rockets) to get to the mansion as fast as possible.
An extra sword enchanted with Smite or Bane of Arthropods allows you to kill any common hostile mobs that spawned in the mansion quicker.
A trident enchanted with Riptide makes travel even faster during storms.
An anvil to repair your tools (required if doing the "Here's Johnny!" tactic).
A few golden apples for quick healing cover.
Can be substituted for enchanted apples.
Healing or regeneration potions for faster health recovery.
A few strength potions for the upper hand in combat.
A few shulker boxes and an ender chest for easier transportation of items.
A few ender pearls for quick escape, if necessary.
A few stacks of harming arrows or poisoned arrows for easier elimination of enemies.
A few invisibility potions for unnoticed infiltration.
A flint and steel, preferably enchanted with Unbreaking, if you want to burn down the mansion. The unbreaking enchantment increases the durability of your flint and steel since the mansion is huge.
A bell can be rung to outline the evokers and vindicators nearby, giving them the Glowing effect that makes them visible through walls.‌[Java Edition only]
A few blocks of iron and a few carved pumpkin to spawn Iron Golems which can be a distraction to the vindicators and evokers and assist you in battle. The iron golems won't attack you if you accidently hit it.
A few name tags to name a vindicator "Johnny" so other mobs in the mansion can distract it.
A sheep and a few Blue Dyes to dye the sheep blue and using it to distract the evokers.