Partnerships are evil, and now you know
If you we're a corporation, he should have resigned as director and had very little say in what's going on as he would require your vote to allow him to become one again.
Moreover you could have blocked dividends so he got no money from the business and he would simply be an "investor" you could have bought out. Or you could than force him out by canceling his shares too
Don't forget he'd be liable for 50% (if this is his share or whatever his share is) of the income tax payable too so he could be in all sorts of trouble if you made a profit, and he only filed a return based on his group certificate from a paid job with an employer
Once again this has huge implications for yourself too, and you need to seek advise on what you can do to have the partnership agreement canceled and/or have him struck off your partnership ABN. (Note that he is still liable for past income tax obligations when his name was on the ABN).
The ATO doesn't look kindly on partnerships where one party in that partnership has outstanding obligations, and if your ex-business partner didn't lodge his recent return with details of the business income he could be in all sorts of trouble if the ATO catches it.