Conrad Murray to Jackson Family -- Mark My Words, I Will Destroy You ... 'Consider This an Imminent Nuclear Warning'

You want the truth? YOU CAN'T HANDLE THE TRUTH!!!

At least that's what Dr. Conrad Murray is saying to AEG and the Jackson family, claiming he's prepared to drop a nuclear bomb on the entire wrongful death lawsuit if he's forced to testify ... a bomb that neither side can begin to fathom ... and that will blow both sides out of the water.

It's the second time Murray's threatened AEG and the Jackson family with destructive testimony, suggesting he's been keeping a bombshell secret for years regarding Michael and the singer's true relationship with his family -- but the latest threat is borderline scary.

Murray made the threat in a recent voicemail message to a friend, pleading with AEG and the Jacksons for one last time to leave him in peace and spare him from testifying.

He says, "Please stop. If you don’t, let this serve as my final warning to both sides. Don’t incite me to testify. Consider this as an imminent nuclear warning. Enough is enough." He then hints at the nature of his "nuclear" secret.

Murray was subpoenaed to testify in Katherine's $40 billion lawsuit against AEG -- but he pled the 5th because he doesn't want to incriminate himself in any upcoming legal proceedings ... after he appealed to overturn his manslaughter conviction.