Hrid +res -atk, What should I do with him?

Are you planning to summon more on the banner? You might end up getting another copy if you do. If you don't, I'd use him even with the bane. Unless a unit drastically needs DC, I wouldn't fodder him.

https://fireemblem.gamepress.gg/q-a/i-pulled-hrid-what-do-i-do

He's fine. I got an even worse one with -atk +hp.
He won't be destroying teams, but Hrid is a solid unit no matter the IV.
Just as long as you use him smart.