This series picks up where the first ongoing Deadpool Vol.1 series left of. It starred another Merc with a Mouth named Agent X, whom was long thought to be Deadpool. It lasted for a total of 15 issues (originally slated for 12, until Marvel added 3 more issues as a kick off to the new Cable & Deadpool series). It was in the final 3 issues that it was revealed that Agent X and Deadpool where in fact different persons.
Collected EditionsDeadpool Classic vol. 9 (#1-6)Deadpool Classic OmnibusDeadpool Classic vol. 10 (#7-15)
— Description from Comic Vine community (comicvine.gamespot.com · https://comicvine.gamespot.com/agent-x/4050-10925/).