LEGION
The son of Professor X! A godlike Omega Level Mutant! A man with daddy issues!
David Charles Haller is and has been many things, including an X-Man (Literally). His power is the ability to generate any power, making him potentially the most gifted mutant of all.
One of the most compelling aspects of David is his ongoing troubles with his mental health, and the superpowered struggles that come along with them.
Though he's seemingly disappeared after the establishment of Krakoa, hopefully the strongest Mutant to grace the Marvel Universe returns!
(Seriously, if they continue to ignore him after all three seasons of FX's Legion it'll be criminal.)
Recommendation:
X-Men Legacy (2012) by Simon Spurrier