Question: what are the best enchantments to fight the wither?
Answer: Smite V is a good enchantment to use against the Wither as it is an undead mob. Enchant a bow with Power V, Infinity, and Punch to do extra damage. Flame is ineffective against the Wither. If you are using a crossbow, enchant it with Quick Charge III, and Multishot or piercing.