Disagreeing in itself isn't necessarily bad, as it's sometimes the only way to find true faults in an idea or implementation. You have to decide if the things

Disagreeing in itself isn't necessarily bad, as it's sometimes the only way to find true faults in an idea or implementation. You have to decide if the things you're disagreeing about, are fundamental things. If it's just difference of opinion (just like no two developers seem to have the same coding style), you have to move forward. But if it's something related to how the company itself will be managed, then you probably will have real difficulties. If you think the management of the company will suffer from this, your options are to quit or hire someone to do your job (and probably retain a stake in the outcome yourself, e.g. remain part owner, or have an agreement to be given some IPO shares).