Scabbards had individuals that ranged from like officer level to commander level, Supernova were all like commander to commander+, Yamato felt like a mini top tier, Luffy eventually got to a point where he could fully go toe to toe and had very equal exchanges with Kaido despite the differences in their stamina. Luffy was the only one to really offer any challenge, everything else only really served to make Kaido waste energy while also transporting the island. Imu overwhelmed post Wano/Egghead Zoro and Sanji effortlessly, casually took down Loki who at the very least is comparable to emperors if not greater than most (though he’s wounded to some degree prior to fighting), and defeated a full health Luffy without any effort. No one had pushed Imu to the point of even needing to use regeneration. The difference is absolutely clear.