Okay, so this is one of those topics where 'strongest' can mean a dozen different things depending on which lore you're pulling from. Theological hierarchy? Military power? Raw metaphysical essence? Makes my head spin sometimes.
In the most straightforward biblical sense, Michael is often seen as the commander of God's armies, the one who defeats the dragon. That's a pretty strong claim to the title right there. The Book of Daniel calls him the 'great prince' who stands watch. So if we're talking battlefield supremacy and divine authority, Michael is the classic answer.
But then you have traditions, especially mystical ones, that put Gabriel up there. Being the primary messenger, the one who announces the Incarnation—that's a different kind of strength. It's about being the direct conduit for the most world-altering news. Some Kabbalistic texts treat Metatron as supremely powerful, transformed from a human prophet into a celestial scribe of unbelievable stature, but he's more of a contested, niche figure.
Honestly, I think Raphael gets overlooked. In Tobit, he's a healer and guide who operates undercover. That kind of subtle, restorative power that holds reality together from the inside feels, in a way, stronger than just smiting things. Strength isn't always a sword. For me, the 'strongest' might be the one whose function is most essential to the cosmic balance at a given moment.