Make the next version of you expensive to underestimate.

Being underestimated is only a cost when it turns out to be accurate. The point is not to prove people wrong for the satisfaction of it, but to build enough real ability that misjudging you costs whoever does it. That happens quietly, through skill that holds up under inspection rather than through announcements. It also frees you from needing to correct anyone in advance.

Stop defending your potential in conversation for a while. Put that energy into the part of your work that would be hardest to fake. Let competence do the arguing when the moment eventually comes.