There isn't a way to defeat it but you just need to go through the waves till' the end.Only them will you be free to go to the next level.
How to obtain Articuno:
Train 6 Ice type pokemon to level 100 Un-hacked and articuno will appear to battle him.
If all your 6 Ice type pokemon are Shiny, Articuno will give you a shiny Baby Articuno.
If all your 6 Ice type pokemon are Shadow, Articuno will give you a shadow Baby Articuno.
If all your 6 Ice type pokemon are normal, Articuno will give you a normal Baby Articuno.
If your 6 Ice type pokemon are Shiny and/or Shadow and/or Normal, Articuno will give you a Normal Baby Articuno.
~Articuno~
