User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20161128063206/@comment-10330822-20161129073548

Except the Heavenly Dragons were supposed to be stronger than the past Satans, not necessarily the current Satans, especially the Super Devils like Sirzechs and Ajuka, who are in the world's Top 10. So when it comes the Heavenly Dragons' lore, you have temper your expectations that the Satans were weaker than what we are used to seeing from Satan. Rizevim, who Issei defeated, was stronger than his father for example. Meaning Issei is probably at least as stronger as one of the original Satans now.

Chances are Indra is stronger than the past Satans. After all, he is the King of Hindu Gods, he is probably stronger than most other Gods are as well also, especially among the Hindu faith. Is he strong enough to defeat any God? Probably not. However, he is definitely one of the top tier Gods, especially with the sealing or deaths of so many of the other Gods.

I've always viewed the cease fire agreement against the Heavenly Dragons as having more to do with removing the other factions from attacking one another so they could focus on Ddraig and Albion, rather than it being a necessity in order to beat them.

Indra probably could have defeated either Ddraig or Albion, but he couldn't do so with his enemies at his back.

Another fact we need to kind of except that Issei and Vali are evolving past Ddraig and Albion. So saying Indra is stronger than Ddraig, doesn't mean Issei can't beat him.