Michael's possible death!!!
But we neither saw his death nor his dead body.
I guess/ think he is still alive.
One day Michael will return to his family!!!!!!!!!!!!!!!

well the MiSa's last scene that was also Mike's death... so sad....*crying*

wen he dead....nuh...n dem had others too dat was touchin bt chhhhhh i hope dem got anodda eps. wid he ALIVE!!!!

I don't consider michael death as sad and when you saw his last msg as clip, somehow our love for micheal increases and i don't think that happy ending will connect us with micheal then his glorious death

The whole thing with Mahone and his son getting killed.That was so sad.

The moments after Bellick's death.

So many! Definitely the tombstone scene with Lay It Down Slowly playing.
When Merilyn got killed/discovered. :-/
(When watching it a second time, because you know what is going to happen,) Tweener writing Aloha on the back window.
When T-Bag killed the doctor.
Both Tweener and Haywire's deaths.
The fact that Westmoreland's daughter most likely died and Michael never got to pass on her father's money/love.
When T-Bag saw the name tag or business card of the fake salesman and realized he would never be "that guy".
When Bob, the CO got killed during the riots when he was almost free.
But I think the saddest for me, second to the tombstone, was the day Lincoln was going to get executed. Especially when L.J. was telling him about his dream.

Definitely,the end of the fourth seazon!I was really disappointed,but I hope Michael is still alive :)