User blog comment:B214/Question and Answers 6/@comment-99.235.66.221-20161130072057/@comment-29963364-20161214035958

Issei could potentially turn out similar to Vasco Strada. He uses raw power to solve everything, and is considered an "Absolute Power Monster."

Attack: Cut/smash through everything in your way with brute force.

Defence: Stone-wall everything, or do the same thing mentioned above.

Speed: Run stright at the enemy before they can react.

Magic: Nutralize it by hitting specific points of the Magic Attack, and watch it dissipate into nothing.

If Issei follows Vasco's example, he could counter everything Vali can throw at him, and completely overwhelm him.