He would have to have been hiding some crazy potent conquerors haki this whole time because based on how the story writes devil fruits vs haki it wouldn’t make sense otherwise. You can’t force your abilities on someone without a powerful haki and you can’t resist abilities without powerful haki. Blackbeard surpassing Xebec, defeating Shanks, absorbing Imu, seriously threatening Luffy doesn’t even add up even if he had ten fruits unless he is a mighty conqueror. Especially if people have him usurping Imu you’re gonna need some Joyboy level stuff.