Trevor

Not really sure why there is a problem with Gohan's transformation, he has trained under the sayians, the namekians, and the kais. He's had his potential unlocked by both the namekians and the kais. He's fought side by side with the strongest of numerous universes and been pushed to his limits by them as well. He has felt good ki and as we have learned sometimes that's all they need to find that path or something similar.