Everyone knows how powerful Claire is in general, but I think her sig. ability is very underrated. For certain matchups, it's exceptionally useful and Powerful. So as her sig. ability description says "When receiving damage that would knock her out, Death Touch is consumed instead and Claire gains a Death Immunity Buff, preventing death and healing X% of her max health over 4 seconds." It is important that this could be triggered multiple times in one fight and also it interacts her general ability to gain power when she is immune to "death".
https://www.youtube.com/watch?v=gRKvXV8z2Dg&t