If there was a boss that you could fight for real, or if the devs even tried a little to give a satisfying final battle, then you wouldn't find the boss on this list. This is for the real dregs. I'm not a picky man, so only the most egregious examples even generate a blip on my case. We count them in no particular order; these are some of the saddest battles in recent memory.
Ganon [[]
None of that infamously bad Phillips CDi game is good - but the final battle could be one of the worst things ever. The series is known for having some pretty memorable final encounters with Ganon. He's turned into pig-monsters and more in his role as a longtime protagonist, and this time he's barely fighting.
All you need is a magic book. When Link violates Ganon's lair, all you have to do is throw a book directly at Ganon's non-canon face, and it instantly beats him. No life bar, no battle, nothing. Oddly, the book you need to throw is described as containing the "Secret Method" to defeat Ganon. I think someone got confused - the book is supposed to explain how to beat Ganon! It's like hitting Dracula with the Bible to defeat him. It does not mean anything!
Lambent Brumak [[]
is a triumphant sequel, a game that fundamentally improves everything about the original. Heck, in some ways this lame final battle is an improvement over the insanely boring final boss of. But I'm a jerk, so I put in for his wet noodle of an ending battle. At least had!
After a fun final mission where you will go crazy with a T-Rex sized monster attached to multiple machine guns, you will escape a huge crater and "fight" an awesome monstrous transformation. The Lambent Brumak looks cool, but there's a reason I'm putting "fight" in quotes. You're stuck in a turret, and it's your job to shoot this poor thing until it dies. That's all.
I'm not even sure it could kill you. What appears to be a final battle turns out to be a dud. According to the developers, all the art of the last boss was complete, they just ran out of time when it came to adding the "battle" to the final battle.