I'm guessing it's "Challenge Tier Clears (Gold) V" because there are way fewer timed challenges with bronze, silver and/or gold rewards than there are challenges without a time limit, but also gold is by design the hardest to beat in time out of them.

I guess the only way anyone can earn this legitimately and consistently is if they do every weekly challenge because those are always timed to my knowledge which would take 4.791239 years on average and that's not taking into account their skill level (which may stop them from getting a gold on any numbers of levels) or any levels that get featured and get a timed challenge (Like Casa de Galunga).

What do you think? Am I right or is there an achievement even more rare? Potentially "Meet a Creator" could be insanely rare if the game gets more popular. Taking Minecraft for example, meeting Notch or Jeb on a server takes some legendary luck.

The secret achievement in the half life 3 collab event(upcoming)

wuts that?

i dont think theres even been enough challenges to get total challenge clears IV yet. and technically silver challenge clears are the rarest currently, because casa de galunga only has gold tier and somnium presentpalooza only has bronze tier, but there are no challenges that have silver but don't have bronze and gold, so there is 1 less available silver clear than other tiers. another fun fact is sapling quest fall festival doesnt have a cleared tier which i think is the only challenge without one