The king! The colonists all through the Declaration and the 27 Grievances state that one of their main reasons for leaving is the fact that the King is taxing the colonies without representation. In fact, the entiretly of the 27 Grievances is essentially a break-up letter...the colonies describe here, and in the Declaration, how they refuse to be oppressed any longer with the rules of a king, and how they refuse to pay taxes that are imposed that they don't agree with.
I hope this helps!