Giants were models to be used in the Minecraft Survival test, but for some reason, they were abandoned. Giants have the appearance of a Giant zombie, but use the sounds of the player damage. They will not attack the player, as they will only approach him and stop within about 5 meters of him. Giants have 50 hearts total and can be very hard to kill. If you make a hole, and make the Giant to come it, so that it will not drop, and going to that hole and jump to it's feet you can get damage from it.
Spawn it in middle of some trees then build walls around it (30 or 20 in average).