  In this paper we revisit the analysis of the ringdown frequencies in the form
of quasi-normal modes for Schwarzschild,Schwarzschild de-Sitter and
Reissner-Nordstr\"om space-times. We plot these frequencies, using the
third-order WKB semi-analytical method against the mass, charge and
cosmological constant for each corresponding space-time for various different
spin-fields. We verify the stability of each black hole solution, including the
extremal Reissner-Nordstr\"om space-time. Finally, we discover four different
traits for the Schwarzschild de-Sitter space-time: i) the frequencies vanish in
the extremal case; ii) the frequencies swap behavior before and after the
extremal value; iii) indication that the naked singularity is stable for
positive mass; iv) for the naked singularity case, there exists a cut-off mass
in the scalar-field perturbation which depends only on the multipole number
$\ell$.
