My 3's team is 2 irl friends, one who's high silver/ low gold and one who's high plat. The enemy team were 3 plats. We got stomped incredibly hard early, especially poor Kennen - we pushed them away from our nexus tower twice, by the skin of our teeth! They kept fighting with tower aggro on them, which gave us the damage to even the odds. After that, we managed to win fight after fight, with their comp doing less and less damage and us doing more and more as we came back. We ended up having to ace them four or five times to undo the damage they did to us, but that victory screen was the most satisfying I've seen in a long, long time.
AND IT'S RANKED SO IT COUNTS
Edit: holy shit I had 100% kill participation!