I'd have gone into academics right at the outset, and not wasted time on management. Or I'd have taken a rat-race career more seriously, and kissed some asses, buttered a few bosses and kowtowed on time and out of time, and focussed on reaching the top, to the exclusion of all else.
There were lots of actions I would have taken differently at different times. I wouldn't have left my aerospace job, but would have waited out the idiot who was chairman of the large public sector corpse and ex officio my chairman as well. I wouldn't have cheeked a chairman who was about to give me a job, I wouldn't have upset another by questioning her impulsive actions. I would have held on to my Hungarian operations as part compensation for salaries not received. I would have got everything in writing, and checked direct with the board before trusting my chairman and going ahead on an ambitious growth plan. And, in general, I wouldn't have lent anybody five rupees. One rupee.