Home is one of my favorites too! My absolutely favorite is 'Love is Lonely' which I think could stand to get some more love, it is not only my favorite Nmixx song but one of my favorite K-Pop songs overall and I was a bit sad when it wasn't on the set list for the tour. You could argue that Nmixx's entire discography is underrated, especially early songs like O.O that got a lot of hate but is actually really good - and 'Cool'!
For Itzy I think most Midzy agree that 'Imaginary Friend' deserves more attention but it just didn't catch on with the general public. It definitely had a lot to do with promotions, even though it was advertised as a dual title-track 'Gold' was clearly promoted as the "main" song. Ironically I heard all the members prefered Imaginary Friend but the company didn't think it was lively enough so they pushed Gold which no one really cares about. Goes to show companies should listen to their idols more often, they're the ones invested beyond just getting their next paycheck.
Also let me ramble off some Twice B-sides that people should listen to: Brave, Behind the Mask, Cactus, Love Foolish, Queen, SOS, Stay By My Side. Some of them are less underrated than others but I'm terrible at gauging these things, I think almost nobody remembers 'Stay By My Side' but it's such a cute-happy song to me that I listen to often!
Also this one by Sunmi;