A properly fitting slip collar or martingale is the appropriate collar for an Akita. A slip collar should be snug enough to just barely fit over the head so that it does not slip down to the base of the neck.
A buckle collar is great for identification but should never be used for walking your Akita as they can easily slip out of them. Harnesses are not a safe means of handling your Akita as not only do you not have control of your Akita, but they can escape from them.