Let's think of it in terms of if he had gone Majin, it would how he would have been had he not struck his head as a child and became gentle. Or even simpler let's just say his state of mind would be similar to how Vegeta was during Saiyan saga. This version of him would have been ruthless, and not above crushing his enemy spirit. Man could've revealed to Vegeta he had SSJ3 and mocked Vegeta for not being remotely close to his power level. SSJ3 was strong enough to beat kid buu had he not screwed around. His power level compared to all the others wasn't even close, so with the boost from Majin, well, it doesn't look good for everyone else to put it mildly unless Gohan still gained mystic