How to reconnect a relationship with a professor
I think you have gotten yourself into a pretty deep mess if it is really as bad as you suggest and not just a sense you have of the situation. But, the only way to proceed is to go visit the professor in person and steel yourself for whatever occurs. I'd make an appointment first, to give the other person a chance to think about their own response. 

You may well owe an apology, so prepare to give it. But, as long as the prof isn't a monster, it may well turn out better than you fear. But it may also take a while to completely dispel any bad feelings if they exist so a single meeting may not turn things around like flipping a switch. But a face to face meeting will give both of you a sense whether a continued professional relationship is possible and desirable. 

It may be the professor was disappointed when you left, but also possible that he/she is so busy generally that it didn't register too much. 

The past is what it is and can't be changed. The future is up you you. But expect that the transition may be uncomfortable.