What is the last stage of erosion

2 answers

This depends on the type of erosion and cycle you are referring to.
Its called the "old stage"

In this stage the gradients are gentle and the velocity is low. Accord­ingly the river lose most of its erosive power and flow in a sluggish manner. In old age a river has maximum meandering. The river at this age does little of erosion and transportation but is mostly engaged in deposition. This stage is characterised by the development of distribu­taries and the river flows almost at the base level of erosion.