Te dejo uno que saque de un video:
/summon Giant ~ ~7 ~7 {Fire:20000,ActiveEffects:[{Ambient:1,Duration:2147483647,Id:14},{Ambient:20,Duration:2147483647,Id:11}],Invulnerable:0,Riding:{id:Ghast,HealF:3000,ActiveEffects:[{Ambient:1,Duration:2147483647,Id:14}],Riding:{id:Giant,ActiveEffects:[{Ambient:1,Duration:2147483647,Id:14},{Ambient:1,Duration:2147483647,Id:11}],Riding:{id:MinecartSpawner,SpawnRange:30,MinSpawnDelay:3,MaxSpawnDelay:1,SpawnData:{TileID:87,Time:1,DropItem:0,Riding:{id:"FallingSand",TileID:87,Time:1,DropItem:0}},EntityId:"FallingSand",SpawnCount:1,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:268,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:254,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:240,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:226,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:212,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:198,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:184,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:170,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:156,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:142,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:128,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:114,Riding:{id:MinecartSpawner,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:100,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:86,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:72,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:58,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:44,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:30,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:16,Riding:{id:MinecartSpawner ,CustomDisplayTile:2,DisplayTile:17,DisplayData:5,DisplayOffset:2,Riding:{id:Silverfish,ActiveEffects:[{Ambient:10,Duration:2147483647,Id:1}],Attributes:[{Name:generic.followRange,Base:20}],HealF:100,ActiveEffects:[{Ambient:1,Duration:2147483647,Id:14},{Ambient:1,Duration:2147483647,Id:12}]}}}}}}}}}}}}}}}}}}}}}}}}}