X-men, who is the best?

In the X-Men series, the five-level mutant "Fung Wong-Nui" should be the best among the X-Men. Although she was ended by Wolverine in the movie, in fact, one is that she is merciful, and the other is that Wolverine can heal herself quickly and get such a result. The remaining mutants can only be rated as Grade 4. These are just movies. There are many five-level mutants in comics. The x-men are owned by Marvel Comics. In the Marvel universe, there is also a five-level mutant who is a "crimson witch" with strong ability. Thanos, who can repel five gems with one hand, crush spiritual gems with one hand, kill Ultron with one hand, and open the enchantment to control the fate of others. It is also the strongest existence in The Avengers.