Today I have made a one command blood system! This only works on players.
Whenever you take damage, blood comes out!


Command:

summon falling_block ~ ~1 ~ {Block:stone,Time:1,Passengers:[{id:falling_block,Block:redstone_block,Time:1,Passengers:{id:falling_block,Block:activator_rail,Time:1,Passengers:{id:commandblock_minecart,Command:gamerule commandBlockOutput false},{id:commandblock_minecart,Command:fill ~2 ~-3 ~-1 ~6 ~-1 ~1 stained_hardened_clay 14 hollow},{id:commandblock_minecart,Command:fill ~2 ~-2 ~-1 ~6 ~-2 ~1 stained_glass 14 0 stained_hardened_clay},{id:commandblock_minecart,Command:setblock ~1 ~-3 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"-=-=-=-=-=-=-=-\\\",\\\"bold\\\":true}",Text2:"{\\\"text\\\":\\\"Destroy\\\",\\\"color\\\":\\\"red\\\",\\\"bold\\\":true}",Text3:"{\\\"text\\\":\\\"Machine\\\",\\\"color\\\":\\\"dark_red\\\",\\\"bold\\\":true}",Text4:"{\\\"text\\\":\\\"-=-=-=-=-=-=-=-\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"fill ~ ~ ~-1 ~5 ~2 ~1 air\\\"},\\\"bold\\\":true}"}},{id:commandblock_minecart,Command:setblock ~1 ~-2 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"-=-=-=-=-=-=-=-\\\",\\\"bold\\\":true}",Text2:"{\\\"text\\\":\\\"Grim's\\\",\\\"color\\\":\\\"green\\\",\\\"bold\\\":true}",Text3:"{\\\"text\\\":\\\"Blood\\\",\\\"color\\\":\\\"dark_red\\\",\\\"bold\\\":true}",Text4:"{\\\"text\\\":\\\"-=-=-=-=-=-=-=-\\\",\\\"bold\\\":true}"}},{id:commandblock_minecart,Command:fill ~3 ~-2 ~ ~5 ~-2 ~ chain_command_block 5},{id:commandblock_minecart,Command:setblock ~3 ~-2 ~ repeating_command_block 5},{id:commandblock_minecart,Command:blockdata ~5 ~-2 ~ {auto:1,Command:/scoreboard players set @escore_damageTaken_min=1] damageTaken 0}},{id:commandblock_minecart,Command:blockdata ~4 ~-2 ~ {auto:1,Command:/execute @e[score_damageTaken_min=1] ~ ~ ~ /particle iconcrack ~ ~1 ~ 0.4 0.4 0.4 0.1 20 force @a 152}},{id:commandblock_minecart,Command:blockdata ~3 ~-2 ~ {auto:1,Command:/scoreboard objectives add damageTaken stat.damageTaken}},{id:commandblock_minecart,Command:setblock ~ ~ ~1 command_block 0 0 {Command:fill ~ ~-3 ~-1 ~ ~ ~ air}},{id:commandblock_minecart,Command:setblock ~ ~-1 ~1 redstone_block},{id:commandblock_minecart,Command:kill @e[type=commandblock_minecart,r=1]}]}]}]}