First would have to be I was too young and totally irresponsible with My Gali Nuva set. The pieces were everywhere and my Mom made me throw it away. Now I don’t own a single Toa Nuva, I wish I would have at least kept the Kanhohi.
Second would be losing Chirox’s Kanohi. It still bugs me after moving rooms twice I never found it again.
My biggest regret is not jumping on the bandwagon in 2001! But that couldn’t be helped, so my real biggest regret would be not buying Vezon and Kardas, I saw them once, and decided to pass, and never saw them again. To this day it’s the only set I’m missing between 2005 and 2010.