In Jain Dharma, the greatest path for reducing bad karmas is the Ratnatraya — Samyak Darshan, Samyak Gyan, and Samyak Charitra.

If you ask for the single highest principle, it is Ahimsa with pure right conduct, because all karmic bondage is weakened by:

• non-violence
• self-control
• forgiveness
• pratikraman
• samayik
• detachment

Among all spiritual practices, the real destroyer of karmas is inner purity of the soul through right faith, right knowledge, and right conduct.

So, in short: Ratnatraya is greatest, and Ahimsa is its living expression.