User blog comment:Trihexa/Top 10 Most Powerful Beings In The World (Unofficial)/@comment-31137559-20170418034800/@comment-29963364-20170418041017

I think Yuuto knows about Sirzechs' [Form of Destruction], and how powerful it is. So since Yuuto said that quote with the current Satans in mind, I think we can assume that Indra is that strong.

Although I still stick to the idea that Indra less a "powerful being", and more a "strong fighter." Like how Sun Wukong could be one-shot by Issei and Vali (pre-DxD), but is capable of defeating Ultimate-Class Devils with ease.

Remember, Indra is a "War" God. Meaning his strength comes form his skill and prowess as a combatant, not his pure power alone.