one of the easiest ways is Soak, it makes it very quickly take damage due to the field, generally it's bulk and the field is what makes it so strong, you can use many gimmicks to take it out if ya dont wanna use stat debuffs on it, everything from Destiny Bond or FEAR to Soak will do the job and hell Soak is a level up move on pokemon found very nearby (the water near the waterfall has wild mons that learn Soak)