Place a fully explored Map into an Item Frame.

Defeat an Evoker.

Cook and eat a pork chop.

Eat nothing but Kelp for 3 days.

Gather all 16 colours of Wool.

Kill a Mob while wearing the same type of Mob Head.

Power a Furnace with Lava.

Create an Iron Golem.

Bribe a Dolphin.

Stay underwater for 2 minutes.

Throw diamonds at another player.

Build some bookshelves to improve your enchantment table.