@Kayriel
I don't think training is as big a problem as you say, though. He isn't training in his physical abilities at all and he isn't breaking people like eggshells. He isn't cratering the ground with every step.
The fire spell straight up was with no training to control his energy at all. And the elf was a fu**ing idiot for doing it that way, because she's responsible.
There's ALWAYS a 'sensing' or 'controlling' part to elemental magic in isekai unless they have a 'status' or some modifier that increases the sensing to 'natural'. Like that series where the mc has every type of magic stat at 777 times his base. He got the power, but he also got the control.
Your complaint is a catch-22, though. If he never even attempts to train himself...well... Go read 'Man of Steel, Woman of Kleenex'.