Since youre asking silly questions like this, I think its safe to assume you dont read the story or intend on it. Shanks has a shallow sea mark from Imu (Big bad guy) and was his slave. His mind could alter be altered and his body controlled like the rest of the gods knights. He allowed his arm ro be taken away as he had already rebelled against the world government by stopped them from getting the Gomu Gomu fruit (Nika fruit). To protect Luffy and the fruit, he cut off the world government surveillance system that was attached to that arm.
@AnimeArenaxr So instead without any evidence Loki is stronger than the Yonko? We are making assumptions based on evidence. What evidence supports Loki being stronger? None.