Board Thread:Questions and Answers/@comment-28905095-20170216140705/@comment-26335978-20170221181715

I myself have tested many methods of defeating the Wither, and I have found this method to be most successful.

Mine down to the bedrock layer and make 3-5 tunnels that are 1-3 blocks wide, 2-3 blocks tall and 75-100 block long. Line the ceilings of the tunnels with obsidian. Make a room at each end of the tunnels, one for spawning the Wither and one for retreating to if your health gets too low. (Optional) Put a dispenser every 10 block and fill them with splash potions of instant health.

Shoot at the wither with arrows of instant health II from a safe distance until the wither is at half health. Drink a potion of strength II and a potion of regeneration I. Charge at the wither. If you're health gets below 4 hearts retreat or eat an enchanted golden apple. Do this until the wither is defeated. You will probably want to have enchantments on your armor and weapons although I have done it without enchantments.