5. Sauron
Ok, hear me out. Yes, it was a pain in the backside getting all the way to Mordor. Yes, the ring raiths are terrifying, the orcs are relentless and the uruk-hai are vicious. However, Sauron is just a helpless eye that can be defeated simply by throwing his jewellery into Mount Doom, a volcanic cavern in his hometown, Mordor. It's a hell of a journey, yes, but if saving the world takes a lot of walking, you walk. Then it's a fairly simple task of getting a few willing soldiers to stand in front of the Black Gate. Sauron isn't too bright and can only look in one place, which will inevitably be at the battle. Then you walk a bit longer while absolutely nobody tries to stop you and throw it in, then get out sharpish. Frodo tried to cock it up at the last minute and still managed it, plus you get an eagle ride home. Worth it.