Spawn the Wither.

Collect Dragon's Breath in a Glass Bottle.

Enter an End Portal.

Use a saddle to ride a pig, then have the pig get hurt from fall damage while riding it.

Breed two cows with wheat.

Use planks and sticks to make a sword.

Use planks and sticks to make a hoe.

Use Shears to obtain wool from a sheep.

Relieve a Blaze of its rod.

Play a music disc in a Jukebox.

Construct a Dispenser.

Acquire diamonds with your iron tools.