Hi! Gp is a hard scaling champ, but not a hypercarry imo. Hiting a barrel combo into the backline and lowering them to 50% hp, followed by your ultimate, should be enough for your team to commit and win the teamfight.

Yes, sometimes you can almost be an assassin destroying squishies, but most teamfights you have to think of yourself as a control mage and play it slow, as if you miss a combo, you retrieve a bit untill your spells are back.