An impact driver is the best tool for loosening stuck nuts and bolts. But not everyone has this power tool or might find a need to have one at home. So, your best choice for loosening a bolt would be a combination wrench with a box end. This can twist in the same plane as the head and has better grip. You can also apply more torque without damaging any mechanism. And if it still won’t budge even with all your tugging, you can pound on the combo wrench with a small mallet.