In 2023, the event runs from April 12th to April 19th.
You simply need to defeat the Bunny boss 10 times over the event.
If you are attempting to get the other items of the event, you will easily achieve this without trying.
If you are only after the cheevo, there are 3 ways to beat the bunny 10 times:
- wait for the timer zero,
go to your currently highest level biome,
break enough blocks to be able to summon the bunny
- spend picks to accelerate/negate the time counter (mine needed 13.4 bn picks per)
- spend some runic dust to accelerate/negate the time counter
(you can either earn them by normal play or by buying them with real money)