Is the Qur'an Alone Sufficient for Muslims without the Hadeeth (Statements, Actions, Tacit Approvals of the Prophet Muhammad)
No, it is not sufficient.
Evidence from the Noble Qur'an
{And We have sent down unto you (O Muhammad ) the reminder and the advice (the Qur'an) that you may explain clearly to men what is sent down to them, and that they may give thought}, {Soorah an-Nahl, verse 44]
Evidence from the authentic Sunnah
((Indeed I have been given Qur'an and along with it that which is like it)), [Transmitted by Abu Daawood]