Which opiate is noted for having a very high high?

Heroin is known for producing a very high due to its rapid conversion to morphine in the brain, which activates the brain's opioid receptors. This leads to intense feelings of euphoria and pleasure, often referred to as a "rush." The potency of heroin, along with the speed at which it acts, contributes to its high potential for addiction and abuse.

Fentanyl is also a powerful opioid, but it is typically associated with pain management rather than recreational use in the same context as heroin. While codeine and morphine are significant in their own right, especially in medical applications, they do not elicit the same level of euphoric high as heroin, which is often sought after by users.