El Gigantes are humans that became giant after an unknown mutation caused by Las Plagas.
 How to fight
The best way to kill a Gigante is to shoot it in the head with a powerful weapon like a Shotgun, TMP, or Magnum. It should also be noted that a Rocket Launcher is a one hit kill on the creature, and fragmentation grenades do heavy damage to it. After it takes enough damage from being shot, the creature with fall to its knees and its Las Plagas will be exposed. At this point, he player can run up to the creature an press the appropriate buttons during the quick-time events to slash the plaga, dealing heavy damage. Repeating this three times will kill it.
Related ThreadsSeeking Help With El Gigante in Ch. 2:3!!! - last post by @ May 26, 2006
Ganados or El Gigante? - last post by @ Oct 25, 2010
The part with the two El Gigante ogres... - last post by @ Mar 30, 2007
El Gigante - last post @ Nov 16, 2005
The Wolf and El Gigante [spoilers] - last post by @ May 10, 2012