had a hard time playing a bad guy
If you had a hard time playing a bad guy, you must mean playing as Roland and Lilith in BL1 right?
Jack was not a bad guy. He had greed issues sure, but a lot of what he was doing was establishing defenses and protecting Pandora. Being double crossed by Roland and Lilith pushed him over the edge, causing him to be the villain in BL2.
Really he was no different than any Vault Hunter. They go from planet to planet in search of Vaults, for loots and power, and they kill anyone who gets in their way. Jack often tried to reason with people who were settled in areas he wanted to explore or mine etc, usually throwing money at them. The Vault Hunters just shoot their way through problems.
Jack is the real hero.