The actor made that shocking revelation while he was on Sirius XM's "Jim & Sam Show" ... where he talked about a period in his life when he was not the successful Hollywood actor and producer he is today.

GE recalled struggling with his mental health and finances in 2008, and admitted he wondered if his kids could collect insurance money if he hired someone to take him out.

Giancarlo said he even ran some ideas by his ex-wife, Joy McManigal.

He said ... "I started scheming. If I got somebody to knock me off, death by misadventure, [my kids] would get the insurance. I had 4 kids. I wanted them to have a life. It was a hard moment in time. I literally thought of self-annihilation so they could survive. That's how low I was."

While Giancarlo seriously considered plotting a murder-for-hire plan, he ultimately chose not to pursue it for the sake of his children -- "I started to think that's not viable, because the pain I would cause them would be lifelong, and there'd be lifelong trauma that would just extend the generational trauma I'm trying to move away from."

Not long after this low point, Giancarlo landed his villain role on "Breaking Bad" ... which he said helped turn things around for him. The actor -- who's promoting his new AMC show, "Parish" -- has been booked and busy the last 16 years ... landing jobs on "Better Call Saul," "Dear White People," "Godfather of Harlem," "The Boys" and "The Mandalorian."