I'm currently working on my Monotype flying team and I realized my Archen has a downsize to his excellent typing for my team. So I was wondering if there's a way to counter this?
It seems the only way to go around it is to just hope the opponent will use Skill Swap or find a Cofagrigus/Yamask with Mummy. Yeah, Archeops can't learn Skill Swap. Of course, you can always use stat boosting moves but by the time you get to attack your Pokemon will probably have fainted. So sorry, Defeatist was meant to murder Archeops. x3
Hope I helped. :) Source: http://pokemondb.net/pokebase/71673/is-there-a-good-way-to-use-the-ability-defeatist