Weight distribution, base suspension settings (caster/camber etc) are the obvious ones.
But even if you say take a corsa and set the geometry to exactly the same as a clio (Ive had a clio and a corsa both running on EXACTLY the same geometry front and incredibally similar rear) it still wont handle anywhere near as well.

The way that the arms are located plays a massive part, as it changes how things alter when the car leans or brakes etc.
A key one different between the clio and corsa b for example is how toe changes during compression. If you compress the suspension on the clio, the toe doesnt change much, but on the corsa it does, so when you turn into a bend and the car rolls the change in suspension settings on the corsa hinders it from cornering as well.

Massively complicated subject though and one I only have a very basic knnowledge of TBH


My corsa xe and clio 172 are very very similar on paper, similar weight, not massively different weight distribution (corsa slightly more nose heavy but no a huge amount), they have same wheelbase and track more or less, static suspension settings are the same.

Its only really the things like steering arm location and bottom arm setup that make such a huge difference to the way they each handle. And sadly that is just about the most difficult thing to change on a car really! Easier to put a different engine in or whatever than start trying to alter the location of the rack and the type of bottom arm setup used etc.