Which opioid is known for being more potent than codeine?

Morphine is a powerful opioid that is substantially more potent than codeine. It acts primarily on the central nervous system to relieve pain, making it a critical medication for managing severe pain, particularly in clinical settings. Morphine's potency can be attributed to its strong affinity for the mu-opioid receptors, which are the primary targets for opioids in the brain and spinal cord.

In contrast, the other substances listed, such as acetaminophen, ibuprofen, and aspirin, are not opioids and do not work through the same mechanisms as morphine or codeine. They are classified as non-opioid analgesics or nonsteroidal anti-inflammatory drugs (NSAIDs) and are typically used for mild to moderate pain relief rather than for severe pain management. Therefore, morphine stands out as the correct answer due to its classification as a more potent opioid compared to codeine.