agent x is alex hayden, a mercenary with a healing factor more powerful than wolverine's. at the beginning of the series it was hinted (because of his personality) that he was deadpool, but this was untrue. it was later revealed that agent x was a combination of deadpool, black swan and nijo. this meant he got memories from all three. he was later able to recover his own memories and get rid of the others'.
i haven't read the series so this is all i know.