I also think the eternals are undervalued. Two of my favorites are Sersi and Makkari.
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This guy is the fastest speedster in the MU, and is a million times better than Quicksilver. Marvel doesn't really have a lot of speedsters, so he could fit a niche. Sure he's wearing a red outfit, so some people might just assume he's a rip-off of the Flash, but Marvel and DC have been ripping each other off forever.
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Sersi, the lovely lady in green, is a magic user so powerful that Zuras, the prime eternal, is afraid of her. She was a bomber jacket wearing avenger in the past, and she could be again. The MU only has a handful of magic users, so there's room for her as well.
My main impression of them came from Gaiman's eternals mini which still reads pretty well after all this time, and I really like the characters.