Suppose that there is a specific instance of a graph for which the approximation ratio of an algorithm polynomially increases with the number of nodes of the graph, say the approximation ratio is $n^2$. Further, suppose that the number of nodes of that bad instance can be easily increased. For example, assume that the approximation ratio $n^2$ is obtained when nodes are distributed over the circumference of a circle and the number of nodes can be arbitrary large.
Then, is it correct to say the approximation ratio is unbounded? When an approximation ratio can be called unbounded?