What Pokémon do you feel you owe an apology?

This is something that's been on my mind as I've been (very slowly) comparing every Pokémon in a head-to-head gauntlet to build my ultimate ranking/tier list. Maybe you unthinkingly went along with popular opinion on a widely disliked Pokémon despite not really understanding the hate. Maybe a lack of viability led you to judge a design more harshly than you otherwise would. Maybe it was the opposite and you disliked a design so strongly that you refused to acknowledge its mechanical strength. Or maybe your tastes have just changed and you now love a design you used to despise.

Whatever the circumstances, I want to hear about unexpected favorites, redemption arcs, and grudges that were finally let go.