Not just 100% of voters, but 100% agreement from ALL the people that the resolution directly concerns.
For example, in the case of the election of a national president - if one single citizen abstained from voting, no president would be elected. If a president is elected regardless of negative votes, it becomes coercion - as the national democratic system in which he or she takes office is first based on the forced removal of resources (tax).
It can be assumed that if a citizen engages the democratic apparatus (by voting) they have given consent to follow its outcome, and also retroactively acknowledged, in part, the legitimacy of previously siezed tax. I think of it like a contract of sorts.
If however, they do not vote, then no clear intent has been demonstrated, and by extension - no "contract" can be assumed.
The previously removed tax should be promptly returned and the non-voters should be exempt from government laws except when on government owned property - while also being exempted from government priviledge (like social welfare, etc.).
In this light, the common saying "if you don't vote, you don't have a right to complain" seems quite redundant. In fact, the opposite is true (not that you should waste your breath complaining about politics)!
It's worth pointing out that democracy in itself is quite a decent and moral system for working out final decisions within groups - but it is only legitimate in the cases where dissenters can be excluded from its cost.
If 3 out of 4 customers prefer Coke to Pepsi, and a local shop can only afford to stock one or the other - for them to stock Coke in order to serve the 3 to the neglect of the 1 is fine, because the 1 Pepsi fan can bring their business to a different shop or even start their own shop altogether!
If however, the 1 Pepsi fan was forced to still buy Coke even though they don't want it - that would be obviously wrong. To suggest the Pepsi fan will still get the benefit of Coke, and therefore still be forced to pay for it, would be rightly seen as ridiculous...
Even if the 1 Pepsi fan actually enjoyed Coke, and therefore benefited - it would still be incorrect to assume that forcing them to pay for it is legitimate. You can't first do someone a favour and then make them pay for it after. Though the Pepsi fan may have enjoyed the Coke, they would prefer to enjoy a Pepsi.
The moral solution is to neither force a person to pay for something, nor provide them with benefit. Only favours that demand nothing in return, without agreement, are legitimate.
Anyway, my friend responded that for such a government system to require a unanimous vote would be pointless - that the government would never get anything passed - to which I responded, "wouldn't it be marvelous".
I was semi-joking at the time - but as I thought about it more recently, this deeper implication became clear to me.
It seems that if you did remove the ability for the government to disenfranchise a minority, by acting in the interest of the higher scoring vote (and against the lower scoring vote) - democracy disappears.
Does democracy exist solely to legitimise the overuling of the few by the many - an inverted monarchy?