User blog comment:Mar-Vell2/Lunella Lafayette Is The Smartest Person In The Marvel Universe??/@comment-16461120-20160803193017/@comment-24812000-20160804152603

@KingAnton yes but even though everyone THINKS that Reed Richards is dead, he is still alive making him the 2nd smartest. Hank Pym might still be alive as the current Uncanny Avengers story arc hasn't been resolved, so he could still be the 5th smartest.

On another note, I'm not actually sure that Xavier was considered one of the smartest. He may have been like 9th or something, but when they gathered the eight smartest people of the time in like 2009's Incredible Hulk #601, Xavier was not among them.