25We’re Only Here For The Weather
First up, it’s beloved Fire-type Ninetales. While this thing is super popular for its design, it struggled to make much impact on the competitive scene due to its sub-par stats. It was relegated to the lower tiers, where it looked pretty darn likely to stay.
Several generations later, it was given
one heckola of a boon in the form of Drought, an ability that sets up instant sunlight when it enters battle. The popularity of the weather archetypes meant that it was suddenly an OU contender, purely on the strength of that ability.