Pokémon Regrets in general have been talked about a fair amount if you type “regret” into the search bar
www.elitefourum.com/t/what-do-you-regret/29266/1
www.elitefourum.com/t/collection-regrets/16589/1
www.elitefourum.com/t/what-is-the-one-sale-you-regret-the-most/14602/1
Although not specifically a regret thread this one does have a lot of people posting what they might regret in the future xD
www.elitefourum.com/t/posts-from-the-future/30961/1