If the bolt was extremely tight & was over powering even the special crank holding tool's -

I used to fit the largest breaker bar to the socket & with the breaker bar facing the ground, crank the engine quickly which would snap the breaker bar against the ground shocking the bolt & loosening it.

It's very suprising how much torque there is to be had in a starter motor!

It's alittle bit rough & ready but work's effectively without damaging anything.