6IV Pokemon are just the tools. You have to build and use them correctly.
Make sure every Pokemon on your team works well with each other. For example, if your Pikachu has a weakness to ground-type attacks, make sure that you have a flying-type 'mon or a Pokemon with the levitate ability to switch into after predicting an earthquake. Also make sure that you have enough coverage (move types) to take out anything that comes your way.
You should edit your post and include a list of the Pokemon you're using, their moves, natures, abilities etc and all of that important stuff so that members can give you advice on how to improve your team.