Hello again! This command by machinegun (https://minecraftcommand.science/profile/machinegun) is for 1.11.2 and adds a pretty much unkillable Blazed Wither (read the comments @ https://minecraftcommand.science/commands/47211) that you can kill in a fraction of a left-click with my god items. Good luck fighting it in survival mode without them!
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 ~8 ~-1 ~2 stained_hardened_clay 9 hollow},{id:commandblock_minecart,Command:fill ~2 ~-2 ~-1 ~8 ~-2 ~2 stained_glass 13 0 stained_hardened_clay},{id:commandblock_minecart,Command:setblock ~1 ~-3 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"Spawn.. The Blazed Wither\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"/summon wither ~ ~1 ~ {CustomName:\\\\\\\"BlazedWither\\\\\\\",CustomNameVisible:1,Tags:[\\\\\\\"blazedWither\\\\\\\"],Invul:2,Attributes:[{Name:generic.maxHealth,Base:10000}],Health:10000.0f,Glowing:1b}\\\"}}",Text2:"{\\\"text\\\":\\\"\\\"}",Text3:"{\\\"text\\\":\\\"\\\"}",Text4:"{\\\"text\\\":\\\"\\\"}"}},{id:commandblock_minecart,Command:setblock ~1 ~-2 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"Click to activate/\\\",\\\"color\\\":\\\"green\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"scoreboard players add @e[type=armor_stand,name=TogAct,c=1] vlqfAz_A 1\\\"}}",Text2:"{\\\"text\\\":\\\"Deactivate machine\\\",\\\"color\\\":\\\"red\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"execute @e[score_vlqfAz_A_min=1,score_vlqfAz_A=1] ~ ~ ~ blockdata ~ ~ ~ {auto:0}\\\"}}",Text3:"{\\\"text\\\":\\\"\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"execute @e[score_vlqfAz_A_min=2] ~ ~ ~ blockdata ~ ~ ~ {auto:1}\\\"}}",Text4:"{\\\"text\\\":\\\"\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"scoreboard players reset @e[score_vlqfAz_A_min=2] vlqfAz_A\\\"}}"}},{id:commandblock_minecart,Command:setblock ~1 ~-1 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"Click to DESTROY machine\\\",\\\"color\\\":\\\"red\\\"}",Text2:"{\\\"text\\\":\\\"\\\"}",Text3:"{\\\"text\\\":\\\"\\\"}",Text4:"{\\\"text\\\":\\\"\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"fill ~ ~-2 ~-1 ~7 ~ ~2 air\\\"}}"}},{id:commandblock_minecart,Command:summon armor_stand ~3 ~-2 ~ {CustomName:TogAct,Marker:1,NoGravity:1,Invisible:1}},{id:commandblock_minecart,Command:scoreboard objectives add vlqfAz_A dummy},{id:commandblock_minecart,Command:fill ~3 ~-2 ~ ~7 ~-2 ~1 chain_command_block 5},{id:commandblock_minecart,Command:fill ~7 ~-2 ~1 ~5 ~-2 ~1 chain_command_block 4},{id:commandblock_minecart,Command:setblock ~7 ~-2 ~ chain_command_block 3},{id:commandblock_minecart,Command:setblock ~3 ~-2 ~ repeating_command_block 5},{id:commandblock_minecart,Command:blockdata ~5 ~-2 ~1 {auto:1,Command:/execute @e[score_witherTime_min=100,score_witherTime=100] ~ ~ ~ /summon tnt ~ ~ ~ {Fuse=80}}},{id:commandblock_minecart,Command:blockdata ~6 ~-2 ~1 {auto:1,Command:/execute @e[type=Wither,name=BlazedWither] ~ ~ ~ execute @a[r=5] ~ ~ ~ setblock ~ ~ ~ lava}},{id:commandblock_minecart,Command:blockdata ~7 ~-2 ~1 {auto:1,Command:/execute @e[type=Wither,name=BlazedWither] ~ ~ ~ particle flame ~ ~2.7 ~ 0}},{id:commandblock_minecart,Command:blockdata ~7 ~-2 ~ {auto:1,Command:/execute @e[score_witherTime_min=50,score_witherTime=50] ~ ~ ~ /summon Wither ~ ~1 ~}},{id:commandblock_minecart,Command:blockdata ~6 ~-2 ~ {auto:1,Command:/scoreboard players set @e[tag=blazedWither,score_witherTime_min=100] witherTime 0}},{id:commandblock_minecart,Command:blockdata ~5 ~-2 ~ {auto:1,Command:/scoreboard players add @e[tag=blazedWither] witherTime 1}},{id:commandblock_minecart,Command:blockdata ~4 ~-2 ~ {auto:1,Command:/scoreboard objectives add witherTime dummy}},{id:commandblock_minecart,Command:blockdata ~3 ~-2 ~ {auto:1,Command:/execute @e[type=Wither,name=BlazedWither] ~ ~ ~ execute @a[r=3] ~ ~ ~ /summon area_effect_cloud ~ ~1 ~ {Particle:crit ,Effects:[{Id:20,Amplifier:2,Duration:200}]}}},{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]}]}]}]}