A murdered ex-con is resurrected and blessed with the power to heal. He must learn to be a saint when others would rather him be a sinner.

I think the original logline is pretty good - I agree that I want to hear who the "other" are.

My go at it:

"A murdered ex-con is resurrected and blessed with the power to heal. He must learn to be a saint; his old gang is determined to keep him be a sinner."

"Old gang" is very specific.
"Keep him a sinner" implies that he was indeed a bad guy when he was murdered. I think his arc is more dramatic if that was the case.

As dpg points out, what art the stakes?

Thanks for the feedback, here is a rewrite of the logline.

A murdered ex con is resurrected and blessed with the power to heal. He must now become a righteous man but his former criminal colleagues wish to drag him back into his old ways.