Materials Required

Cheats enabled

Steps

1. /give [your name] minecraft:commandblock 1

2. Place Command Block.

3. Set Command Block's first option button to 'Repeat'

4. Set Command Block's third option button to 'Always Active'

5. Set Command Line to say 'kill @e'

Congratulations! All life has been extinguished! Revel in your new status as the lord of a dead world, from your lovely (dead) view of your spawn point.

DISCLAIMER: Astrotrap are not responsible for any damage caused to the playability of your world, to the livelihood of your chicken horde, or to the livelihood of your chicken hoard.

You could also do /kill @e[type=!Player] in order to become the reigning king of your barren realm

Or do this

/setblock ~ ~ ~ minecraft:mob_spawner 0 replace {EntityID:"PrimedTNT",MinSpawnDelay:0,MaxSpawnDelay:0}