This Article Contains Spoilers - WARNING: This article contains major spoilers. If you do not wish to know vital information on plot / character elements in a story, you may not wish to read beyond this warning: We hold no responsibility for any negative effects these facts may have on your enjoyment of said media should you continue. That is all.
The Sleeper is the climatic boss battle of Captain America: Super Soldier and one of Zola's first major world-threatening devices, a colossal robot of unthinkable might designed to be a testimont to Zola's mad delusions of a world where the limitations of humanity are erased via the domination of "flesh" by machines.
The Sleeper's main goal is to destroy the Allies and ensure HYDRA's victory, which would allow Zola to continue his insane experiments and like many robots it is not necessarily an "evil" being but rather a weapon of mass destruction being utilized by the wrong hands.