Ah crap, I should suggest actual stories too, huh?
Azarinth Healer leaps into first place.
Crap, I can't remember others off the top of my head. Take this.
www.scribblehub.com
If you're going to use Azarinth Healer, then I guess by the same logic that makes Ilea immortal we would have to also put Luna from "The queen of darkness does not want to be the villain" on the list.
(She can heal herself from the exact same kind of normally instantaneously fatal injuries that Ilea can.)
And, while we're going on the track of nigh-unkillable due to super healing, let's go with Vandaleu from "The Death Mage" as well. He has death magic that delays death, which allows his vampiric healing to fully heal any normally fatal injury. After that, he just stops using his delay death magic because he doesn't need it anymore. So, on that note, he actually is a level above Luna and Ilea.
(Especially because, unlike those two, he has the ability to think with his soul. He doesn't have the weakness of being temporarily helpless until he can heal if someone destroys his brain. Although, the very fact that all 2 out of 3 of these characters have the ability to fully recover from the complete destruction of their brain should be saying something already (Luna can survive decapitation, but not brain destruction.) But, unlike Ilea, Vandaleu has the ability to continue taking actions even while his brain is still destroyed. Ilea's body will stop moving until her brain recovers.)