Such a scenario is indeed possible. For example, I know several countries where the law allows the authorities to strip a recently naturalised citizen of their citizenship if they have been found guilty of a terrorism-related offense but do require that the person still has another citizenship.
At the same time, it does not mean that renouncing other citizenships would necessarily protect you in all cases. Having a citizenship is indeed broadly regarded as a human right (cf. article 15 of the Universal Declaration of Human Rights) but human rights law has little teeth and you can easily find examples of loopholes or countries just ignoring this principle. Finally, some countries do not allow their citizens to renounce their citizenship at all.