Minecraft wiki entry for kill, associated text: To kill the player executing the command: kill @s
To kill the player Steve: kill Steve
To kill item entities: kill @e[type=item]
To kill all entities within 10 blocks:
JE: kill @e[distance=..10]
BE: kill @e[r=10]
To kill all entities except players: kill @e[type=!player]
To kill all creepers within 10 blocks:
JE: kill @e[distance=..10,type=creeper]
BE: kill @e[r=10,type=creeper]
To kill all arrows that are stuck in a target: kill @e[type=arrow,nbt={inBlockState:{Name:"minecraft:target"}}]