I once watched a stream exactly on the Minecraft website, perhaps from a dev', long time ago.
He got the diamond pickaxe and told that the thing you need to do after finishing that "achievement" is to look for lava and Self Delete like a boss.
Or something along the lines, eitherway, he said that, dug down, died in lava, and ended the stream.
If anyone remembers what the link to the stream is please tell me.