I believe that the best way to get this achievement is to play a green/black deck with elves INCLUDING NISSA VASTWOOD SEER. Black is added for removal spells like murder and a few critters with deathtouch. Play solo so on easy, use the elves to build up blockers and do not attack unless you know you can deal damage without losing a creature and knowing you still have good defense. an ideal hand will have at least four lands in your hand with nissa vastwood in it also. once you get it out protect it and play its +1 ability to look at top card each turn until you get enough counters on it to make 6 lands 6/6 creatures. More than likely you will control the board by this point. Keep their stuff at bay and when you know you can get at least 4 creatures through attack with everything and it should pop.