In a previous Question it was argued that it would be impossible to add enough charge to a black hole to make it pass the extremal black hole limit since adding charge would increase the mass of the black hole due to the electrostatic field energy (and thus mass) that would be added as the charge is added.
Note that an electron cannot be a black hole but if an electron were a black hole it would be a super-extremal black hole per this wikipedia article: Basically the Schwarzchild radius for the electron's mass is $r_s = 1.35 \times 10^{-57} m$ whereas the charge radius of the electron is $r_q = 9.15 \times 10^{-37} m$. So since $$\frac{r_q}{r_s} \approx 10^{21} \gt 1$$ an electron, if it was a black hole, would be a super-extremal black hole by a large margin. In words, the electrons mass is completely negligible compared to its charge.
An uncharged black hole can be constructed out of matter at any given mass density by simply constructing a big enough sphere of that matter. This is true because a sphere of radius $R$ with a constant (low?) density will have a mass $M$ that is $\propto R^3$ whereas the Schwartzchild radius is $\propto M \propto R^3$. So as $R$ increases the radius of the sphere will eventual be less than the Schwartzchild radius.
So, can we make a super-extremal charged black hole by using a very large sphere of radius $R$ that is made out of electrons uniformly distributed with (low) charge density $\rho$?