D. Gray Man
The crux of Claymore centers around Clare and other Claymores hunting down dangerous monsters, or Youma, that threaten the populace. D. Gray Man functions on a similar premise as Allen and other Exorcists are sent to take down dangerous monsters known as Akuma, that can take on the form of humans. In truth, Youma and Akuma are uncannily similar, and D. Gray Man has plenty of dark themes to match that of Claymore.
Both anime feature a white-haired protagonist with exceptional abilities, and a strong cast of supporting characters to back that up. Even the two series’ settings are similar taking place in a Medieval-style world. The key difference here is that Claymore has just a tad more violence and profanity. The similarities are uncanny, however, so you should absolutely check out D. Gray Man if you’re yearning for more Claymore.