Welcome to GTP, Deliverator! Enjoy your stay...
I haven't driven the GT One, but that's a characteristic of big-boost turbo cars. You get on the gas, and the turbo spools up, and *wham*! You're in the weeds.
Try to be gentle on the gas, and maybe stay in a higher gear.
It's better to learn how to deal with oversteer, than it is to put up with understeer. Oversteer can be balanced if you are careful, but understeer means you're taking a trip off the outside of the turn - period.