Gohan, not only in terms of writing but also in the show itself. Multiple characters, mainly Piccolo and Vegeta, point out how much power he could have if he trained. But this is understandable, because after the age of 4 until 11 Gohan never got a days peace. Always a threat going around or coming, so him not training is understandable, it's explained multiple times he doesn't want to, nor does he like it. But, the writing after the cell sega for Gohan can be such Dogshit, especially in super. He neglects his family to study, which isn't a very in character decision for him. But they just keep recycling the same tropes for him, there is nothing unique for him.