Here's the text from the Kirchen-Gesangbuch:
I. Lobet den HErrn, ihr seine Engel, ihr starken Helden. Halleluja.This is most of Psalm 103:20: "Bless the LORD, O you his angels, you mighty ones who do his word, [obeying the voice of his word!]"
R. Die ihr seinen Befehl ausrichtet. Halleluja.
Where the ESV has "you mighty ones," the German has "ihr starken Helden," which I would translate as either "you mighty heroes" or "you mighty champions." In French, it's "invincibles porteurs de ses ordres," which combines this with "who do his word" ("die ihr seinen Befehl ausrichtet") and which I would translate as "invincible carriers of His commands."
When I lookt up this passage in the STEP Bible, I discovered that the Hebrew simply uses the adjective "mighty" as a substantive. The ESV follows this, but both the German and French translations provide a noun for "mighty" (or "invincible") to modify.