I don't think you can really complain about spoilers in a topic marked "Worst game endings".
Borderlands is certainly up there in terms of terrible endings. "Hey you've just spent a ton of time and ammo fighting through all those dudes, here's the legendary vault full of riches and stu-LOL JUST KIDDING HERE'S AN EASY STRAIGHTFORWARD BOSS WITH A WEAK SPOT THE SIZE OF THE MOON, NO STUFF FOR YOU!"