Even if we count Asura's Wrath is canon, then it's obvious Asura held back a great deal when he fought Oni Akuma. As he was Mantra Asura when he fought him. But he could still transform into Mantra Reactor Asura and Asura the Destructor. The guy who's energy beams killed stars and planets out of existence, was himself larger than Earth(Gaea), and punched a planet 100 times bigger than him and destroyed it.