Both can read minds. Jean has telekinesis but J'onn has intangibility, shapeshifting and invisibility... so who wins?
__________________ "I realised that there was this incredibly benevolent force that wanted me to know that there was no reason to be afraid... ever." "We don't have to win, we just have to fight."
"There is no way to peace, peace is the way." "Be yourself. Those who mind don't matter, and those who matter don't mind."
If by Phoenix you mean Jean with the Phoenix Force, then the Phoenix literally lobotomizes Jjon Jjonz.
However, if you mean Jean the mutant (and not Jean plus an intergalactic entity) then Jjon Jjonz basically sets slays her psyche! Easy.