Baghdad ? Even in Saddam Hussein’s ruthless regime, “Chemical Ali” stood apart, notable for his role in gassing 5,000 people in a Kurdish village — the deadliest chemical weapons attack ever against civilians.

Ali Hassan al-Majid was hanged Monday, leaving a notorious legacy that stamped Saddam’s regime as capable of unimaginable cruelty and brought unsettling questions about Iraq’s stockpiles of poison gas and whether it could unleash them again.

The poison gas clouds that struck the village of Halabja began what would become an about-face by Washington — which had supported Saddam during the eight-year war against Iran’s new Islamic state in the 1980s, but soon became his arch-foe and protector of the Kurds in their northern enclave.

Al-Majid, 68, was executed about a week after he received his fourth death sentence since facing Iraqi courts after the fall of Saddam. He was one of the last high-profile members of the former Sunni-led regime still on trial in Iraq.