9. Nihilanth (Half-Life)
https://www.youtube.com/watch?v=CTpmtG5UuRE No matter how brave one might be, hearing this overgrown monster bellow out your name upon arrival can be a tad unnerving. Your journey through Valve's legendary first-person shooter had already been like a nightmare, having to go up against countless aliens and even a pesky helicopter, but the final battle against the Nihilanth was your greatest challenge. It was one thing to be mercilessly hunted by the military that had descended upon the Black Mesa research facility, but it was a whole other level of fear to be trapped inside a room with this guy. His large range of attacks culminated in a dreadful teleportation move that would send you to some heinous places, including what can only be described as a platforming nightmare as you had to retake your place on the battlefield in a series of well timed jumps. Fighting the Nihilanth can be humbling, rocking the very core of your skills as a gamer, but it is also one of the most rewarding experiences of gaming bliss ever.