Yesterday, I stumbled across this cover of "Let It Go" by the French deathcore band Betraying the Martyrs.
I'm not even generally that fond of deathcore, but this is well worth a listen. (If the growling vocals put you off, try to at least listen through the first chorus - from that point on, the song does a better job of balancing the harsh and melodic vocal elements.) I like the fact that, unlike many metal covers of pop songs, this isn't just a tongue-in-cheek exercise in seeing how silly you can make a pop tune sound with death growls and palm-muted guitar riffs stuck on it - it feels to me like the band genuinely put a lot of work into making the song work in a different genre. I actually think that if you somehow hadn't seen Frozen or heard the original song ever before, it might never occur to you that this song was not originally conceived as deathcore. Lyrically, it even fits pretty well into a long lineage of deathcore songs about alienation and power fantasy - although on average deathcore lyricists tend to use more swear words and more explicitly violent/destructive imagery.