Interestingly, if someone is constantly offered as underrated, then they probably weren't/ aren't actually. So I'll pick someone no one mentions ( I think) and no one agrees with (LOL) as truly underrated:
The most underrated Dolphin of the last 10 to 20 years is 2014 Offensive coordinator Bill Lazor. He has 1 year to judge him on - 2014, as he stopped being the OC early in 2015, going down with the Philbin ship. 2014's offense was the best of the last decade -easily. 7th DVOA, 10th scoring, top 10-15 by a variety of metrics. (yes it's sad, but that's the best offense we've had). The offense was innovative for it's time, and I think exciting and imaginative. FWIW national power rankings, on average, were the highest of the decade for the Dolphins for much of the year ( not the beginning or the end). The talent, while not terrible, was nothing special, and not much different than most of the last 10-15 years. ( I don't see anyone praising Jeff Ireland's amazing personel moves and drafts of the early 2010's)
So Lazor is either forgotten or considered bad to terrible, but he schemed the best offense in a decade or more for us, even if he wasn't great by any means. That's the stone cold definition of "underrated".