Counter example: Sobolev embedding

Question

We know that $H^1(\mathbb{R^2})$ is not embedded in $L^\infty(\mathbb{R^2})$. Using the fact that $u \in H^2(\mathbb{R^4})$ if and only if $u, \Delta u \in L^2(\mathbb{R^4})$, how can I find a radial counter example of the fact that $H^2(\mathbb{R^4})$ is not embedded in $L^\infty(\mathbb{R^4})$?