User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-2605:E000:160D:8082:5958:1C8F:5DA7:6765-20190704120104

So according to Issei as he witnessed the Indra vs Mahabali fight just one of there attacks was equivalent to his infinity blastsr. Guess we can expect to see Issei’s Great Red form in his match against Indra.