User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-41.13.20.174-20181224141815/@comment-71.221.38.212-20190107204758

Hard to say for sure if they'd be jealous. After all, from the descriptor of Diehauser Belial's Worthless ability, he needs to understand what he's trying to render worthless extremely well or it won't work. They've never said if Diehauser understands all the "after market" upgrades Issei has undergone. As such, if his data is incomplete, the Worthless ability is a no-go. So it may come down to how much Issei knows about Diehauser's combat style not revolving around his Clan's signature skill. After all, knowing your opponent to cripple special skills is much like knowing your opponent's combat style to decode the path to victory.