Created a new world and was flying around to test performance and saw a Guardian Temple, decided to enter it and kill an Elder Guardian and that didn't trigger the [Monster Hunter] achievement. I had to go kill a regular Guardian to trigger the achievement
Thank you for your report!
We're actually already tracking this issue in MC-115750, so I resolved and linked this ticket as a duplicate.
However, that ticket has already been resolved. That means that this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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