Prime suspects would be Slovakia and Austria in this case. My point was slightly different though: this is just one thing where Hungary might have seemed isolated but I’m pretty sure there are other matters where threat of Hungary veto stopped some initiatives before they could be considered in full.
Imagine EU directive making all member states need to recognize same sex civil unions. Hungary would obviously veto it so why would you bother but there’s still Bulgaria, Romania and Poland that could say nothing and hide behind Hungary.