u/GG1312

I was bored

The command is

summon falling_block ~ ~0.5 ~ {BlockState:{Name:command_block},TileEntityData:{auto:1,Command:"setblock ~ ~ ~ activator_rail[powered=true] strict"},DropItem:0,Passengers:[{id:command_block_minecart,Command:"say Success"},{id:command_block_minecart,Command:"setblock ~ ~-1 ~ repeating_command_block{auto:1,Command:\"fill ~ ~ ~ ~ ~1 ~ air\"} strict"},{id:command_block_minecart,Command:"kill @e[type=command_block_minecart,dx=0]"}]}