A good representation of strength in the One Piece Universe is the amount of bounty under one's head. Here are the highest ever bounties revealed in One Piece (as of Chapter 925)
Ultra Instinct is the most powerful (and hardest to achieve) form in the whole Dragon Ball universe. Even the Gods of Destruction stood up out of respect when Goku achieved the form. But truth be told, the form is a failure, and this article will try to answer the reason "why".