The Wall of Flesh(WoF) is the hardest boss in pre 1,1 mode(pre Hard-mode) and can easily ruin many attempts to get souls etc. This will tell you the strengths, weaknesses, and ways to defeat the WoF!
Strengths: Has the Hungry(a Riot Shield), Shoots lazers, Spits Leeches, keeps moving, and doesn't allow access to anything past Molten Armor(Unless you multiplayer)
Weaknesses: Has 3 Huge Hitports, has no defense in 2 of them, the hungry drop hearts, and is slower than the player.
How to kill: You will need a good bow, gun and sword. Preferrably Molten bow(Hellfire Arrows), Minishark or Phoenix Blaster(Silver Bullets), and Night's Edge. You will probably want Molten Armor for the high defense unless you are a great dodger and then you can use Necro Armor for the ranged bonus.
Arena: A long long bridge across the underworld(flat)
Potions:Healing, Grav, and Ironskin.
The fight!: Drop the Voodoo doll at the farthest point of the bridge away from spawn. Then once you know what side the wall is coming from open fire with your gun. When the Hungry get averagely close open fire with your bow and when they can actually touch you use your sword. The gun is what you should use for the rest of the match(unless you need to kill Leeches for hearts) and you should win it! If you get pushed off your bridge just use your bow while hovering so the wall is in the middle left side of your screen. And don't use your melee weapon for anything but the Hungry or Leeches. Have Fun!