The literal meaning of "Infernal Affairs practitioner" is: a monk who practices very diligently without interruption. There is no Bodhisattva or eminent monk in Buddhism who is called "Infinite Walker". If it refers to a specific Bodhisattva, only Ksitigarbha Bodhisattva barely fits the bill. Because Ksitigarbha Bodhisattva mainly saves sentient beings in the "Infinite Hell", of course he is also a "walker". From this perspective, it can also be said that "Infinite Walker" refers to Ksitigarbha Bodhisattva.
"Wu Jian" is the free translation of the Sanskrit "Abi", which means no intermittent breath.
"Practice", in a narrow sense, refers to Buddhists who have become monks but have not yet been ordained, or ascetic monks who walk around begging for food. In a broad sense, it refers to people who practice Buddhism. For example, "Avalokitesvara Sutra": "Read and recite the Mahayana and encourage those who practice it."