the worst ending ive ever seen is bf3's ending
*spoiler* the way he does an high speed race in mid newyork with a nuke in his back seat and no cops or police enforcement trying to stop any of them and then blackburn and makarov goes out to the streets and do an old school beat out until makarov pulls out a 44 puts a bullet in your friends mind and in another guy while there are around 100 people watching you and they dont do shit and then you beat the man to death while again family and kids are watching you do it without saying a word.
*end spoiler* that end was a major turn off for me
the best ending ive seen was in Medal Of Honor 2010 Tier 1, i actually cried alittle when the game ended.
*spoiler* the way that through out the whole final sequence you are not if rabbit survives or not and in the last minute you are filled up with joy that he is alive and bamm he is dead, it got me by such a huge suprise i just started tearing at that moment, even thinking of it makes my vision alittle blurry from upcoming tears.
*end spoiler* i just feel like the people who wrote MOH Tier 1 story did a fantastic job and they really kept the suspense over the game. Touche to them