20 Video Game Bosses You Must Defeat Before You Die

9. Nihilanth (Half-Life)

The Nihilanth is the leader of all the monsters that invade Black Mesa during the events of the brilliant Half-Life, and the finale of the game sees Gordon Freeman travelling to the alien world Xen to do battle with the beast once and for all. Though as a whole Half-Life is pretty challenging as far as FPS games go, the Nihilanth is the zenith of its difficulty, as the master alien fires energy balls at you which can result in a very quick demise is you're not paying proper attention. After working your way through some challenges the Nihilanth hurls your way, you have to dive atop the giant monster's head, and destroy his brain with whatever weapons you have left. This will immediately lead to the famous dilemma G-Man presents to you, of either to join his ranks or to refuse, and in the latter case, you'll be hurled headlong into a battle against Xen monsters that cannot be won.