four opponent powers
The four practices used to purify nonvirtuous imprints on the mindstream. They are: 1) the power of the object, taking refuge in the Three Rare Sublime Ones and generating bodhicitta; 2) the power of regret, feeling deep regret for the negativity committed; 3) the power of resolve, determining not to repeat that negativity; and 4) the power of remedy, a practice such as Vajrasattva that effectively acts as an antidote to the negativity.