$A = \begin{pmatrix} 1 & 0 \\ 0 & 2 \end{pmatrix}$

$A = \begin{pmatrix} -1 & 1 \\ 0 & -2 \end{pmatrix}$

$A = \begin{pmatrix} 1 & 0 \\ 1 & -2 \end{pmatrix}$ with eigenvalues $1, -2$

$A = \begin{pmatrix} 0 & 1 \\ 0 & 1 \end{pmatrix}$