Final answer:
Uranus experiences the most extreme seasons due to its axis being tilted by about 98°, which causes one pole to have 21 years of continuous sunlight and the other 21 years of darkness.
Step-by-step explanation:
The planet that has an axis tilt that gives it very extreme seasons is Uranus. Uranus is tilted by about 98° with respect to the normal of its orbital plane. This unusual tilt leads to dramatic seasonal changes, as each pole gets around 21 years of continuous sunlight, followed by 21 years of darkness. During the Voyager 2 encounter, it was observed that one pole was facing directly into the Sun, experiencing a prolonged summer, while the other was in a long, dark winter. The extreme tilt of Uranus' axis is thought to be the result of a collision with a large object early in the solar system's history.