Quickest
Part of speech: adjective
Definition: Moving with speed, rapidity or swiftness, or capable of doing so; rapid; fast.
Fastest
Part of speech: adjective
Definition: Most fast.
Example sentence: Ambition is to be the fastest runner on this planet, to be the first on the South Pole, which is a grotesque perversion of ambition. It's an ego trip, and I'm not on an ego trip. I don't have ambitions - I have a vision.