Minecraft wiki entry for Defeating_a_pillager_outpost, associated text: An iron/diamond/netherite sword preferably enchanted with a high level of Sharpness, Fire Aspect, Sweeping Edge‌[Java Edition only], and Looting if possible. Avoid using weapons enchanted with Knockback as pillagers wield ranged weapons. You have an advantage if you can keep them close and force melee combat.
A Bow, preferably enchanted with Infinity and a high level of Power and Flame if possible. (Punch can both help and hinder you because pillagers also use ranged weapons).
Several Arrows, multiple stacks if using a crossbow or a bow without Infinity (In Bedrock Edition, pillagers drop arrows, so this is less of a problem), and if you have Infinity, you need only one Arrow.
A full set of at least iron armor, preferably enchanted with Unbreaking and Projectile Protection, or just Protection
A Shield with Unbreaking, or two unenchanted shields (note that pillagers with piercing crossbows can still damage you with your shield raised)
A Crossbow, which can be used instead of or alongside a bow. If possible bring one with Piercing and one with Multishot, both with Quick Charge. Multiple required for machine gunner tactic (see § Tactics below)
Highly nutritious food like Steak, Cooked Salmon, or Cooked Porkchop