[Ke0]

Actually my spoiler was off, since I finally saw the RAW, did anwser a few questions though

Spoiler:

Ed does realize what Greed's armor is made of, and he uses alchemy to break it down. But the breakdown only lasts a few seconds before Greed can cover that area backup, so Ed uses the technique to expose a spot on ED's chest, and stabs him, killing him. Ed didn't know he was going to die die, then Greed explains why. Ed thinks he was joking around until Greed shriveled up haha