What should you do if you don't hear anything back from editor after a whole year from first submission?

If the editor isn't responding, it's time to escalate. The journal's web page should give contact info for an editor-in-chief and/or a managing editor. Contact one or both of them and let them know that you would like an update on the status of your paper, but cannot get a response from the handling editor (include dates of submission, dates you sent emails, etc). They should take care of the situation.

Can you get hold of the editor's phone number? I've sometimes found it very effective to call someone when they haven't been replying to emails. However, I've only done this with academics I knew personally. But it still might be worth trying, before you take the fairly major step of withdrawing your paper after more than a year (the advantage of eventually having the paper accepted by the journal you currently have it submitted to is that the date of submission will be on the published paper, and of course this date will be much later if you submit it somewhere else now).

(It's an old question yes but would like to give another answer) I would seek to withdraw the paper from the journal with a letter to the editor stating the reasons so. I think there needs to be a time where you've 'waited enough'. For me 1 year is too much but for others, perhaps they have more patience and I think for you to be so patient with your to-and-fro to the journal speaks volumes about your character but it may not be so good for your manuscript.

P.S. What was the final outcome of this?