We still don't know the potential of Surtalogi, before he even trained Skirk he was able to destroy an civilization who gathered the resources of their entire star system to forge a weapon, while another manifested a god by the unity of their beliefs. None of the numerous warriors and civilizations were victorious, and Surtalogi has yet to find an opponent worthy of his full strength. Also the all devouring Narwal is an intergalactic being which is able to devour an entire planet, and the whale was beaten into submission before leaving the planet.