According to an info graph on the web that a forum member shared over 1 year ago, Jean Grey's Myers-Briggs Personality Type is the INFJ. The site https://www.16personalities.com/free-personality-test mentions this personality type to be the rarest in the world, which makes sense when the heroes represented by this info graph as being INFJ-types are very 1-in-a-million type of heroes. Having taken the test four times in the past on different sites, I receiving results as INFJ (2/4 times), INFP (1/4), and inconclusive mix between INFJ and INFP (1/4), I consider myself an INFJ-type.
After seeing the chart again, I wanted to poll the Jean community to ask how many of us actually are in this personality type alongside our esteemed Phoenix-clad heroine.
Please remember that a hero's personality can vary based on authors (e.g. Grant Morrison's take on Jean dagger eyes towards Morrison) so remember that even though you might not be in this personality type, in the end, it's not something to take serious and other heroes are fun, too.