Tutorials/How to get rid of a rogue wither

If you spawned a Wither, got killed, and now it's going berserk in a random place, and effectively you cannot enter the area without a major risk to your life? Need to get rid of it? Then here it is, this guide will help you get rid of the wither!

Preparation
If you are fighting a wither you couldn't kill the first time, make sure you are better-prepared this time. Some useful items to bring are as follows:
 * Diamond or netherite armor enchanted with Protection, Projectile Protection, and/or Blast Protection. Unbreaking III and Mending are useful if said armor is low on durability, and Feather Falling IV can help in case you fall. High falls are a possibility if a wither goes rogue.
 * A bow enchanted with Unbreaking III, Infinity and power V. A crossbow enchanted with Quick Charge III and possibly Multishot, or in a pinch, a Trident enchanted with Loyalty III will do as backups, but the bow is your best bet.
 * A diamond or netherite sword or axe enchanted with Smite V. Sharpness V will do in a pinch, but the extra damage against undead mobs is preferable. Only use it at close range, and be prepared to use your bow as your main weapon.
 * At least 10 golden apples
 * Enchanted golden apples if you have any
 * At least a half stack of steak, golden carrots, or other highly nutritious food
 * At least 3-6 healing and regeneration potions
 * At least 3-6 strength I (extended) and II potions
 * A water bucket, slow falling and/or fire resistance potions in case of large falls, possibly into free lava
 * An elytra and several stacks of firework rockets for quick attacks and/or escapes
 * Ender pearls to escape quickly in case of emergency (note that you will take damage, which can be mitigated with Feather Falling boots)
 * At least 3-6 buckets of milk to cure the wither effect (note that it also removes positive effects)
 * Several totems of undying
 * Iron blocks and carved pumpkins to spawn iron golems to help fight
 * Tipped arrow of healing II (optional, are not affected by Infinity which means they run out) or splash or lingering potions of healing II in a pinch, these items will damage the wither as well as heal you and your allies
 * An ender chest and/or shulker boxes to carry extra potions and other items

Note that all of these items are very useful in fighting a wither normally. Taking on a rogue wither is significantly more dangerous, as you may have already been killed once and the wither you attempted to destroy is now running loose in an area potentially made highly dangerous. Withers can fly and will attack any living mob or player with their explosive skulls, and also heal over time, so take extra precaution when approaching. Expect to see it flying, bombarding living animals with its skulls, and surrounded by massive craters stretching deep into the stone, possibly freeing water and/or lava sources. It may be a surprisingly long way from where it originally broke free, so watch for its healthbar.

If you cannot get rid of a wither for whatever reason

 * Make walls or a fence to mark the danger zone, it is a key precaution to not enter as you risk leading it out into the safe zone.
 * Try and contain the wither underground, there will be no mobs to attack and the surface is now a safe zone, however it is still a precaution to not enter the area, as it could go up to the surface and cause more carnage

If you can get rid of a wither
First off, prepare, the terrain is most likely a waste land, and most man-made structures if still standing will not help you, first off, slowly enter the danger-zone, bring friends with you to assist.

Attacking the wither
If the wither is still on the surface, it will notice you, so it is recommended to build a double layered wall and defenses, and build mini bases with underground tunnels to make an escape.

Fight the wither normally, if you fail, keep on trying.
 * Build trenches for when the wither starts to shoot you.