For me it'd be a mastery of Yoga, i.e. enlightenment.
Discussion
What's the highest form of enlightenment? How is it attained?
Through love and grace as you connect with the inner Shabd
Compassion.
Compassion.
Compassion.
The answer to that question is the subject matter of the Gita.
The highest form of enlightenment is the complete renunciation of the duality between the individual and supreme self.
There are several Yoga that can lead to it: action, devotion, meditation, renunciation, etc.
All focus on eliminating that which binds you to your ego until you are one with God.
You are God, and God is you--light of light.