All I can think of are near-villainesses in anime that tend to capture my heart, not that they're necessarily good people, or even make good leaders, but because they're, well, ...
hot.
Like
Mari Kurihara from
Prison School (Hepburn:
Purizun Sukūru). She starts as the chief adversary in the first arc, but ends up a victim of the very system that put her in power when an
underground student council, with even
more nefarious personages as members, takes over. She then becomes an erstwhile and somewhat sympathetic ally of our protagonists. In either guise, she's the sultry confident female leader who brooks no insolence. And she's hot.
The other example is
Rias Gremory from
High School DxD (Hepburn:
Haisukūru Dī Dī). Rias, who should need no introduction to AP fans, is more than your typical bombshell student council president, but is in actuality a devil. Despite her nature and that of her other council members, she's the primary female lead to our protagonist, Issei, and thus she's more of a protagonist from the start than Mari above.
And she's hot.
I'd name more, but the gist of it is,... I have come to expect the best of any student council leader to be... eye candy, if nothing else.